[N8N]

Car is '09 335i E92 6MT, purchased with 72Kish miles, now about 74,500. Car essentially looks like a new car inside and out and runs and drives great with one exception.

So I've been having a heavy throttle (not necessarily full, but "brisk" acceleration) surge that's been driving me nuts, and also when I replaced my spark plugs recently I found #6 black and wet. So I ran a couple tanks full of Techron through the car, not thinking that it would really help, but hopeful... then today since it was a balmy 38 degrees outside I re-pulled the #6 spark plug and found it not as black and not as wet, but still not looking like a good spark plug should. I also pulled #2 for comparison and there was a little black around the edges but the porcelain was still white and it looked about like a good plug should. So I strongly suspect that I have a leaky #6 injector and that pouring stuff in the tank ain't gonna fix it.

FWIW I have no codes.

Called dealership, got a quote for $4-500 to replace the injector, and "about $800" for walnut blasting...!

Wasn't real happy about that. Called my buddy that has a franchise shop and he's supposed to get back to me and let me know if he can code in a new injector (I know he can't walnut blast.) Also left a message for IMA Motorsport in Chantilly and am waiting to hear back from them. I stopped by Mach V yesterday and Dan is the guy that could tell me what they can and can't do, will have to get with him when he gets back from vacation. (can't blame the guy for taking some time off though.)

Then I figured it would probably be prudent to flash back to stock - I've been running Cobb's Stage 1 Aggressive Linear map. So I did. Started the car and there was tons of white smoke pouring out of the tailpipe, and the cooling fan came on full high. Shut down, checked codes, I have no CEL but it was showing code P2EE6 Coolant temp sensor plausibility. Reset code, restarted, *seems* fine but I have not driven it yet. Since I had my battery charger out (I always use a charger or power supply when flashing just because) it's charging now because I figure topping up the battery is always a good idea as much of a juice pig as these cars are. I guess I will try an ECM reset, dump another bottle of Techron in and go from there.

Does this sound to you guys like I probably need both the injector and a walnut blast, as I expect? How can I non-invasively confirm the need for walnut blasting? Any other shops I should call in the NoVA/Dulles area?

thanks!