I have been having some idling issues lately, and had an EcuTEK dealer just do a quick monitoring of the car during idle - basically plug it in while the car was idling and simply look at the roughness monitor, fuel correction and so forth. Fuel corrections didn't go above 0.8% - so that looks good. The car is running slightly rich since the EcuTEK only removed fuel while the car was idling. Overall - all monitors looked good - except for the roughness monitor on cyl#3 - all cylinders were zero during the entire time we sat there with the car idling except for cyl #3. The car has been idling rough for some time - only when the car is warm. The roughness monitor, for cyl#3 only, was jumping around from zero to 5 and a few jumps where it hit 12 once (max).

Question: What are some ideas as to what could be causing the roughness in cyl#3?

My thoughts are:

spark plug (fouling)
coil pack (malfunctioning)
grounding of coil pack
grounding of something else
leaky head gasket in the area of cyl #3 (doubtful?)
bad ring land/ring on piston #3


Mods list (applicable only) - all professionally installed:
GT30R kit (UR)
exhaust side wrapped
Cold air intake with the above kit
PE 850cc injectors
Perrin fuel rails
NGK one step colder plugs
Spearco top mount
Intake airt temp gage with differential readout (takes turbo outlet and throttle body inlet temps - two temp sensors)
Tial 44mm EWG plumbed back into dp
Hi-flow cat
Greddy BOV recirculated back into intake
EcuTEK and UTEC
Full line up of Defi gages for monitoring
Koyo radiator
EcuTECK w/ UTEC