I didn't say anybody was wrong I just tried to give a bit more info on the problem and will check thows things when I get a chance. If its the waist gate were hearing is that normal or is it screwed.
that's the information we need..
If it's the waste gate we're hearing
if it's when the truck is warming up, it's most likely the exhaust back-pressure valve closing..
which is a normal condition, and can cause a "surging" feeling..
the EBPV functions a lot like a heat-riser on an carbureted gas engine.. it closes off the exhaust to put some load on it, and helps the engine warm quicker.
a lot of guys in southern climates gut the thing, but I'm not a big fan of that..
if you hear a steady hiss going down the road under load, or the truck is just flat gutless, look first at the turbo and inter-cooler boots. Look for "dirt" stains on the pipes at where the boots are.. especially if the stains have a greasy or oily feeling.. this is an indicator of leakage, and is fairly common...
just clean them up in a bucket of warm, soapy water, and reinstall them.
another thing to look for is the same "sprayed dirt" stains on the inter-cooler itself, as it's possible to be cracked. Not real common, especially on a 7.3, but a 6.0 or two it has happened on.
finally, the tuner itself could be causing it.. especially if a code for "ICP Above/Below Desired" exists.. this is the high-pressure oil pump (HPOP) running out of oil due to the tuner program.. you could either get a different tuner, a chip, or an aftermarket HPOP..
