Need advise what this might be for engine
 

Ok i got the compression readings off my 2jz GTE motor. Cylinder 5 is at 125lbs and cylinder 6 is at 150. The rest are at 160lbs. The shop noticed brassy color fittings in cylinder 5. What do you think this is. Doesn't sound like a broken piston ring. what do think it may be. Is it possible it may just have a bad head gasket you think.

Do you mean brassy color filings (not fittings)?

Did you notice any damage on the #5 spark plug when it was removed?

Note that the headgasket is made from a much harder metal than the (aluminum) cylinder head. If you have headgasket damage, you'll almost for certain have head damage too.

Most times, too much boost on pump gas damages the ring lands near the valve recess in the piston. Either way, unfortunately, it sounds like you will need some engine work... :(

To avoid low compression and metal filings in the cylinder either 1) run less boost, or 2) run race fuel, or run alcohol+water injection, or convert to E85. That's a hard and fast rule - violate it and the engine will always get damaged from detonation. When fuel detonates, it explodes like C5 or TNT instead of burning like gunpowder. No engine internals...no matter how expensive...can stand up to detonation. The bone stock 2jz-gte can easily put out 1000hp with high octane race fuel, and absolutely no engine damage. With 93 octane {(r+m)/2} pump gas and the oem timing curve, never exceed 16psi (1.12 kg/cm2) of boost.