having an issue on an S5 n/a where the #1 spark plug keeps fouling out after about 10 minutes of idling.

i have already pulled the mid/upper/lower manifolds off and checked the injector clips, they're ok. rebuilt and installed a LIM due to a stuck front 5/6th port. serviced and replaced ALL injectors. inspected and adjusted the throttle body, set the TPS, set the timing. checked for vacuum leaks all over, none present at all. replaced the CAS, replaced the front coil pack, replaced the leading plugs, installed a ground strap from the front rotor housing to the coil pack, cleaned and tightened the battery terminals.

the car runs perfect for a short period and then starts stumbling and it is always the leading #1 spark plug that is the culprit. i'm thinking the ECU may have a faulty front primary injector driver but have no ECUs on hand to swap out at this moment so just looking for any ideas anyone may have.

other notes, this is a brand new engine that only has a few miles on it, from rotary wherehouse i believe the motor came from. the engine compression tests fine, starts and runs fine, but after it stalls out it is a bitch *** ************ to get started unless i let it sit for an hour or clean off the plug then it fires right up. only a very light film of oil on the plug, no smoke from the exhaust so it's not burning oil, even in most cases the plug looks perfectly fine when i remove it but the timing light is telling me its not until its cleaned and reinstalled or replaced.

fuel pressure is fine, even went as far as adjusting the AFM to lean out the mixture but nothing works for more than about 10-20 minutes of run time.

this problem is driving me nuts!

 

made sure that ignition cable is okay?

 

might of forgot to mention that, swapped all the spark plug wires and that particular one several times with a known good set of wires.

i think for kicks tomorrow i am going to disconnect the secondary #1 injector clip to make sure it isn't bleeding power from somewhere.