I have installed the trap oxidizer bypass pipe, blocked off the egr, and cut off the vacuum to the arv. I though I would report on my impressions.

First, a little about my car. It is an 85 300TD that has been well cared for. The original owner had it for about 15 years and 175K. I have some receipts from the MB dealership, including a rebuilt transmission. It languished for a while, and had some work done by the next owners that appear to have gotten in back on the road. The next owner, the one I bought it from, did quite a bit of work on it himself, including rebuilding the self leveling rear suspension, cleaning and adjusting the injectors with a pop tester, and replacing the timing chain. He kept up with valve jobs and oil changes and replaced worn suspension parts.

When I bought it about 3 years ago, it had 265,000 miles on it. Ran good. Starts first crank and stops with a good shake, so I assume the compression is pretty good. I kept up with oil changes and valve adjustments and minor repairs. It now has 358,000 miles. About 3,000 miles ago, I put in new Monarch injectors and set the pop point on all between 2020 and 2050. (the PO said he set his at 1850, but when I tested the old nozzles before replacing them, they were from 1400 to 1640, so I'm sure my settings will drop over time). I tried to, and think I did improve the injection pump timing. It wasn't far off, and I could barely get to the rear bolt to loosen and tighten it about an 1/8 turn each way. The others were loosened and I used a crow bar. The new injector nozzles, set to proper pop and injection timing, along with diesel purge and valve adjustment made the engine run smoother and with quicker throttle response than it had when I bought it. The improvement was dramatic. The car has absolutely no shake at idle. Everyone who has been in it before and after, mentions the difference immediately.

A week before I took out the trap oxidizer, I disconnected the vacuum to the egr and arv, just to make sure nothing untoward happened. I did not really notice much difference. Maybe the car responded to a little less throttle.

So, with my car running so much better than it had probably for 150,000 miles or so, I wasn't expecting too much difference with the test pipe installed in the place of the oxidizer canister. I did not crack open the canister, but it looked like at least 2/3 of the screen at the outlet end was plugged with soot. The EGR and intake from it into the intake manifold were totally plugged with fossilized gunk that I had to chip out with a screw driver. Maybe why I didn't notice much difference disconnecting the EGR. The improvement with the pipe replacing the oxidizer is more dramatic than the new nozzles. The car just wants to GO with minimal throttle. I drive the same road at 45 miles an hour to town every day. I don't need to look at the speedometer. Now, I keep noticing I'm up to 55. there is a half mile long uphill a half mile from my house. The engine is not warmed up by the time I start up it. Now, it goes up the hill faster with half the throttle. My car was never as slow as some on this forum complain of, but it accelerates from a stop much quicker, and from 30 to 60 getting on the freeway like any normal car. I don't push it because it's so old, but I'm sure it would pull right up to 80 with no problem and without slowing down. it breezes down the freeway at 70 and doesn't slow on the freeway hills like it did. I do notice a much richer exhaust smell at idle, cold or warm, but don't see smoke. I can't usually hear the turbo over about 40 mph because of wind noise, but on steep hills in town and the hill a half mile from my house, I can hear the turbo at a much higher pitch, spinning faster, than it ever had before. I haven't had the normal mix of freeway/in-town driving for a full tank since the change, but I'm thinking it seems like I'm probably getting about 1 mpg better, maybe more. I usually got between 26 and 28, depending on if I drive 72 or 68 on my 200 mile weekly trip on the freeway. I'm sure some of my mpg gain is lost accelerating with a bit heavier foot because it's nice to have some get-up-and-go. Finally, when giving it a bit of pedal, there is a bit more serious note to the engine without what was essentially a plugged muffler in front of the turbo.

If your trap or cat oxidizer has 300,000 miles on it like mine did, you have absolutely got to take it out and use Rollguys bypass pipe. The difference in my care is truly amazing, and I think it was probably running better than most with like mileage before the change.

The pipe fit perfectly, but the holes in the flange that mounts to the turbo were not quite completely drilled out. I spent a half hour or so wrestling the pipe and turbo, and even got the crow bar thinking I couldn't get them lined up. Finally, I lifted the turbo off, and found I couldn't push the bolts through the flange. 2 minutes of finishing the holes with a drill, and everything slipped perfectly into place.

the job was time consuming for me. The bolts on the exhaust manifold to the oxidizer, especially the bottom one, are hard to get at. I couldn't even manage to hit it with kroil oil. Took me hours to get it off, trying to get at it from any angle, top or bottom, I could think of. Before you even attempt to get at it, I suggest taking out the heat shield, battery, and battery tray. (even the heat shield bottom screws had my hands cramping up) I ended up having to buy a 17mm crows foot to get two of the bolts holding the oxidizer to the turbo loose. I also ended up having to drain the radiator, because I had some sort of bracket attached to the water pump in the way of one of the egr allen bolts. As soon as I started loosening the bracket, coolant began leaking out. Might as well drain some coolant first, rather than in a hurry after its a little too late. Putting it all back together was easier, because there is a lot more room with a pipe instead of the oxidizer. As a final note, the PeachParts instructions on how to remove the turbo certainly doesn't mention all of the bracing I found holding my turbo on.

All in all, with a trip to town to buy ball end allen wrenches, before learning I still had to nearly remove the bracket to get the egr off, and another trip for the crows foot, it took me two full days, but I'm certainly, and probably obviously not a mechanic, and I spent some time letting kroil oil soak in.

Still, I should have done it years ago.

Next - see what kind of boost I'm getting, and maybe adjust the waste gate.

Thanks for the great product, Rollguy!