I have a 1999 Suburban with a 5.7L "R" engine (151,490 miles). Idles fine usually. Has new cap and rotor. Cylinders 3 & 5 have a bad dry oil foul problem (build-up) after 5k to 6k after replacement. There is also "valve ping" and I use about 1 quart of oil per week and it is driven very few miles. There are no coolant or oil leaks externally. Coolant levels are always consistant and I never need to add any. Compression test results are: all cylinders show 125-135 psi except for cylinder #3. It reads 95-100 psi. MIL comes on and scan tool reads cylinder misfire on #3 & #5. Overall, seems to run okay and doesn't lack power except for going up large hills or mountains. Then it loses power and chugs along.
I have been told: intake gasket, valve stem seals, valve guides, and piston rings. Any of these could be the culprit.
There is no smoke from exhaust pipe on cold start-up and no signs of smoke during hard acceleration on level roads.
The compression readings are most concerning to me.
Need an engine or is there a possible easier fix?
Does anyone have any thoughts on this?

 

If it burns that much oil you need an engine. Do not let someone talk you into anything else or you will waste your money.

 

USMC-LAV: Welcome to the forum.

Good advice above.