Well, the bog down when you launch sounds about right.. I don't know why but on these cars without much mods for some reason if you launch over 2500 the whole front end will dive and then spool back up to normal.

I don't think I have ever heard of a larger dp creating boost problems. I do believe that choodle is running the stock dp though (so that would not apply to him). however, I have several friends who went with a 3" dp and have had no boost problems.