I recently had work done. All the bolt-ons cai, headers, tbe, injectors, fuel rails, fuel pump, boost controller, and xs engineering ign amp. Ecutek dyno tuned of course. But I noticed that over the last week or so the car doesn't feel the same. Yesterday the CEL came on. So I took it to GT Motorsports to have Sam look at it. He said that there is a problem with cylinder #4. He doesn't know if its mechanical or an ignition problem. He said maybe my ignition amp is sending too much power to my stock coil packs. In the five years he's been tuning STI'S he's never used ignition amps. He recommends I remove the ignition amp and do a compression check. If compression checks out ok then he knows its ignition related. It's a 2006 STI with 8500 miles. Could it really be a bad cylinder? What do guys think? The car was never pushed beyond 1.3 bar i.e. 18 pounds of boost, mostly driven 1 bar. How much does a coil pack cost?? All mods where done for FP GREEN coming soon. Please help!!!!!!!!