Don't feel too bad. I agree with the above poster that said modding and getting quicker are separate things. As long as the mod doesn't hurt the learning curve dramatically, i.e. slicks, there's no problem that I see. Going to the track for me is about fun, and it is more fun to drive a faster, better, track car (up to a point I suppose).
And there are people running full blown racecars with little experience too, so no matter what you do you can't be the only guy with that level of mods for your experience level. I hear you on the comparing lap times stuff though, it does make it difficult to compare, if that matters.