Happy New Year to All.I'm new to the group so I'll try to explan my problem best I can.
I have a 1991 d250 intercooled auto with overdrive 135,000 mile truck.Had the pump turned up, 16cm housing, gauges, fuel pin ,new lift pump, but not a govener spring yet.
All went well 6,000 miles or so after the shop tuned the pump, boost 24lbs really fast, it could heat pass 12,000 easy.Had to watch it close.Really felt it in the seat of your pants would spin the tires
Now I loss power and it won't heat past 10,500 boost down hard to get 60 to 65 mph out of it towing 6,000lbs,lost fuel mileage.
New lift pump,can't see any leaks,fuel filter less than 6,000 miles.
Thanks for any help and I'm glad I found this Diesel site.

Have somebody run the accelerator pedal while you watch the linkage. The throttle lever on the pump should hit the high speed stop screw. If it does not, figure out why.

Info on adjusting the TPS is in the sticky.