So, after some serious head scratching, I decided to remove and test the EBP. If it wasn't functioning correctly, eg. the back pressure was higher than it was telling the computer, the variable vanes on the turbo would be in a clamped down position, making lots of boost at low engine loads (what I was seeing)and making lots of backpressure at the same time, like an engine brake, hence the sluggish performance. (man that's a long sentence) I pulled the EBP, and flushed it out with carb cleaner, a fair amount of carbon came out, but it wasn't plugged up by any measure. I put a 5volt power supply on the EBP and measured the response as I applied about 10 lbs of air pressure to it. The voltage increase from about 1v with no pressure, up to 5 volts with about 10 lbs of pressure. Reinstalled it and the truck runs great. The boost pressures are a lot lower cold or warm. I was seeing 10 to 20 lbs when warm, no load under moderate acceleration, now I'm seeing maybe 5 lbs for the same circumstance.
What I figure, is there was enough carbon built up in the sensor to keep it from functioning correctly. Maybe these things need a cleaning every oil change.
On another note, I've always had trouble getting the air cleaner out. My basic proceedure was to take out the battery for better access to the air cleaner, kind of a pain but it worked. This time I took the large rubber accordian boot (the one that's about 6 to 8 inches long and 4 inches in diameter, that connects the clean side of the air cleaner to the pipe that goes to the inlet of the turbo) off first, made taking the air cleaner off a breeze. Give it a try...
Ken
