2003 GMC2500hd 4x4
All stock 156,000 miles 4200 hours.
Front wheel bearing replaced.

PMs done every 5000 (fuel / oil / small tranny)
Air at 10,000
Internal tranny every 20,000

No problems to date, truck used everyday.

Have noticed decreased sound of "compressor spooling up"
Encounter light grey smoke under light loading, something new.
Mileage has fallen off 1-2 on interstate.
Seems like power is not there.

No other problems.

How about some Ideas....

Thanks

:help:

Injectors

That sounds like injectors. From the lose of mileage and smoke that is where I would start. Motor is covered so I would take it in.. Good luck