Narrowing down engine issues (Misfire and smoke)

[TMoreheadS4]

Hey everyone,
I've had some unfortunate news with my '13 8.5 s5. A month or so ago my car began having a conistent misfire. I scanned using my Obdeleven. It showed a cylinder 6 misfire and also the hide cylinder code for it as well. Since I was approaching 100k miles, I figured the coils were due. My plugs were changed about 15k miles ago. I replaced the one coil using autozone, and ordered 6 new with 6 new spark plugs as well through FCP Euro since I get the lifetime warranty. The cylinder 6 misfire went away as well as the hide cylinder. The car ran fine for about a week until I started having the exact same issues, this time for cylinder 4. I decided to go ahead and replace all coils and plugs. The plugs were decently fouled over for the mileage, but I do run a stage 1 tune. After replacing everything, the misfire was still present in cylinder 4. Along with the misfire, the car would smoke pretty heavily on acceleration. No codes were present for anything other than the misfire and hide cylinder. My mechanic stated that before he tears into the engine to see if anyone else has had similar issues and can point to a possible solution. Exhaust and cats are in good shape, and no codes present for an issue with the PCV valve. Any ideas?

[hahnmgh63]

Before you drive it anymore I would get a video inspection camera into cyl 4 and see if the Piston looks cleaner than the others which would indicate a bad injector. A bad injector can wash the lubricants from a cylinder and cause damage.

[TMoreheadS4]

Before you drive it anymore I would get a video inspection camera into cyl 4 and see if the Piston looks cleaner than the others which would indicate a bad injector. A bad injector can wash the lubricants from a cylinder and cause damage.

I am having my mechanic do that this weekend. Hopefully he finds that being the culprit. He's also going to check compression.

[S5.Moe]

I’d bet the s/c cooler or both coolers have failed, are you noticing coolant consumption? I went through the exact same thing, the s/c coolers were leaking into the combustion chamber and causing misfires, obviously check if this is truly your issue, if so, definitely get a walnut blast at the same time