i have a gsr-t with internals and last month i had my car on the dyno for some tuning and after one pull it started to knock in the number one cylender area, we did a compression test and all were within 5psi of eachother. i brought it home ripped the head off and revield that something was sucked in the intake and and made so minor damage to the top of the piston and the underside of the head, to be on the safe side i took the head to a respectable machine shop and they took the valves out and reinstalled them and said everything is fine, i reinstalled the head.
yesterday i had my car back on the dyno for more tuning and it was running like ****, it was spittin g and sputtering and what sounded like misfireing, we did another compression test and found number 1 cylender 20 psi lower than the others so we did a leak down test and revieled that #1 was leaking air by what was determind to be the exhaust valves on the count of the air wasnt seeping by the rings and into the crank case vent and was not seeping threw the intake, but we could here air in the exhaust
my question is, is there anything i should be aware of or should check, any input on what this could be would help thanks

here are the pics of the damage

 

Find out what is getting into your intake. The machine shop should have inspected the valve seats. My guess is that another foreign object entered cylinder #1 or there was debris in the cylinder after the rebuild.

 

what ever was in there was gone by the time i took the head off all i found was what looked like very small metal particals about the size of a grain of sand, i was guessing they were part of the pistons or something, eather way i never found any thing not even in the turbo mani. or the turbo, and i find it really weird that before i took the head off i did a compression check and they were all withen 5 psi of each other maybe ill check the head gasket
anything else i should look for?

 

ttt

 

how does that cylinder's spark plug look?

 

looks good brand new