Hi,
My CEL light came up today when it is cold start (about -5 degrees celcius, and I parked my car outside for over night)! The story is like this, when I put in the key and tried to turn on the car, it needed about 10 sparks in order to get the car started. After the engine started it tumble/shaking and I had not seen this happen before. About one minute later the CEL came on and blinking, and my car still tumble/shaking. I waited for about 6-8 minutes and finally the engine calm down . However, the CEL was turned on now. I tried to turn off the car and turn back on again, but the light was still there. In addition, I noticed that the car rev was a bit lower than normal when warming the car. Before I installed the TC2 v.2.5 the car usually rev at 1,400rpm when it is cold start. Now it just rev at 1,200rpm for the same situation. One more important thing, my car have difficulty in cold start though before/after the TC2. It needs about 6-10 sparks for a start and it is getting worse. So, do you think is there something wrong with my chip or there is a problem of my car? Thanks a lot!

My car is an impreza'99 2.5RS (automatic)

regardless of the cause, you are either running too rich or too lean on startup. Could be a lot of factors. I wonder about maybe the very cold air being denser and causing lean. Either way, try this- on a day you don't have to be anywhere, go outside and crank it just enough a couple of time to where the fuel will flow but not enough to kick it over. Quickly pull a plug and see if there is fuel on it. A bit of a long shot, but might work. Also try adjusting your fuel a little bit at a time with the idle loop. I probably don't need to tell you to enrichen first to avoid ping, but I just did anyway. If you can't tune it out with some shadetree guess-and-check, try having a full diagnostic done. it'll cost a little bit, but it's very likely to pinpoint the source and maybe save some aggravation trying to chase down the cause.