About 1500mi ago my '84 300TD started running rough on diesel at low rpm (below 1500), and stalling at Idle and when in gear. I first tried adjusting the idle screw, but in order to achieve a smooth idle, I had to adjust it too high for the tranny, so I backed it back down. Then I tried adjusting the valves (they were fine), gutting the ALDA, and blocking off the EGR (ball bearing method) and this briefly solved my power problems (and then some , but not the idle problem. The car will not start when hot (above 40°C), and will only start cold with ~10-15sec of cranking with my foot to the floor. Over the last 200mi I have noticed a reduction of power at driving speed. I also tried messing with the rack damper screw on the back of the IP... no effect whatsoever. Here's the catch: it runs like a dream on veggie... Idle is fine, perfect even, shifts into gear nicely, gobs of power on the highway and accelerating from a stop, just wont run worth a ***** on diesel. Here are some of my hypothetical ideas as to why it wont run right:

1) Injectors (one or more leaking or not spraying right) I have never checked them so this might be a start?

2) Rack damper screw (do these things go bad? how do I tell?)

3) Timing.. dont really know much about this, I have heard that due to veggie's high cetane value (near 60) that you can mess with the timing and have them run fine... could my injection timing (I'm guessing this would be start of delivery) somehow come out of adjustment so badly that it wont run on diesel but will run on veggie? How do I go about fixing this?

4) IP bad? Should I pull my IP and have someone who knows bosch IPs look at it? The fact that it runs great on veggie makes me think that this is not the case.

5) Bad lift pump? I am planning on installing a vacuum/pressure guage right before the IP soon, this should tell me whether this is the case.

These are the only things I can think of, seeing as i am almost 100% certain all my valves are switching correctly, and there are no air leaks on the diesel side. Advice from anyone familiar with this sort of problem, timing issues, injector issues, IP issues, would be greatly appreciated.