I'd like to ask an aside question here.

3 weeks ago I purchased an '87 300D turbo, 134K miles. Over tha past 3 weeks of going over it and prepping it for being a daily driver, I discovered that the pressure hose to the wastegate actuator was rotted off at the fitting on the turbo housing. I've since replaced it with some available 1/4" thick wall fuel injection hose.

The drive home from the dealer was 80 miles on the interstate, 65 and 70 mph on cruise control mostly, no romping or gunning it, rpm never saw 3000 for the whole trip. When I arrived home, I topped off the tank and it took less than 2 gallons, approaching 40 mpg for the trip.

Also, there was an excessive amount of oil in the intake boot from the CCV/breather connection. So much there was liquid oil in the boot, and had run down the turbo and side of the engine over time and made it look like there was a significant oil leak on the engine itself, and even backed up into the flapper box upstream of the boot. OIl and crud was built up at least 1/4" thick on the underside of the boot and front of the turbo.

My theory on the oil - excessive boost on output means excessive vacuum on inlet, and it was literally sucking oil vapor out thru the breather hose at a rate the oil separator in the valve cover couldn't handle.

Any feel for what boost levels might have gotten to, given the engine wasn't revved over 3000 rpm, if the wastegate wasn't working?

Given the discussion so far, if the turbo was putting out higher than normal boost due to a nonfunctioning wastegate, and the overboost circuit was keeping the engine defueled to "normally aspirated" levels, could that explain why the beast gave every indication of getting close to 40 mpg on the trip home?

Thirdly, what would you recommend I check to ensure that this didn't do any damage to the engine over time?