Hello,
I have a strange sound coming from my L. It sounds like an exhaust leak but it is really hard to tell. It is really only noticeable when the truck is under a load. Like after it has shifted through all the gears and is going about 45-50 mph and you barely push the throttle in. It sounds like and exhaust leak. I have taken to have it looked at and there are no visible signs of a leak. One tech said it was an exhaust leak the other said possible "spark knock"? I know noises are really hard to diagnose without hearing it but any help would be appreciated.

Thanks, B

 

look out for loose spark plugs. They sound a lot like a header leak gasket or exhaust manifold leak