2002 6.0L Yukon Denali Backfiring thru intake under load...need suggestions

[huston2326]

Sticky valves can also do that. Exhaust valves hanging open when the fuel is ignited can make a pretty good bang in the header!
I would suspect that kind of thing would show up with a cylinder reading low on the compression test...

10-4 Compression test incoming.

 

[rockola1971]

Those bolts aint missing....they are broken. The heads have broken off from heat cycling and corrosion. Very common on the LS series engines. Must be cheap quality bolts GM used on the series.

 

[dnt1010]

10-4 Compression test incoming.

My guess is that you have a broken valve spring, the compression test should identify which cylinder