had 16 lb.pulling heavy trailer,then went 5-6 lb.and barely pulling it home.checked shaft play,it was minimal,what should i do next?

 

on what type of vehicle?

 

Huffing that much boost under those conditions likely blew out a seal/gasket somewhere in the intake tract.
Motor/parts heat up and things move around.
Info please!
What is boost?
Boost is the 'backup' of average blower pressure in the intake tract trying to get into the motor.
If there is a leak, the average goes down.

 

97 f-350 w/7.3,5 speed,4x4,banks turbo,3"open exhaust.

 

check for a leak after the turbo on the intake, possibly a waste gate or blow off valve?

 

Or a rubber coupling on the inlet tubing.

 

its a diesel.....

 

had that problem on my brother in laws car.

 

we used to have a 96 and had the waste gate stick open. had to drive it 100 miles home towing a 30 ft box trailer.