2horseowner said:
I use the C&L kits on both my cars. It's my understanding that a reflash is required to get the maximum performance from the kits. Without the re-flash the computer will eventually retune itself back to factory settings. This was substantiated by running a similarly equipped unflashed car against mine at the track and posting a .6 better 1/8th mile run. I'm a newbie so forgive me for jumping in.
The K&N is the only one as far as I know that does not require a re-tune. I was running it without a tune for the past month and it works great. According to some dyno numbers I've seen 15rwhp without a tune, I didn't dyno mine, but you could feel it.
As far as your experience I'm sure that the difference if the cars where identical could have easily been driver, best way to see if it changed over time would probably be dyno numbers to compare rather than track times where many factors can play into it.
I just installed a tune today and it helps even more, especially with shift points adjusted etc on the auto.