DHP is digital horsepower. 3800performance sells them i think. they are the original PCM guys.

intense PCMs are not bad anymore. they arent as bad as they used to be.

ZZP is very unreliable and their tunes just arent top notch like they should be since they are the leading vendor for us.

never dealt with overkill. a lot of people swear by him, but ive also heard he's pretty slow with response time.