Just installed Gruppe-S V2 header with Jet Hot coating. I wasn't expecting much at all but as very pleasantly surprised. I agree with blackie. Mid-top end is much more enjoyable now and I don't think I can live without it.
I took a long 3 hour highway drive after the header install and I was grining all the way
, So far I have not noticed any lag (if there's any). It was well worth the $549. Btw, I have VF34 and other supporting mods.
For those of you with messy oil change problem, check this out. http://www.fumotovalve.com
It's the second best mod I got for my car! (behind the remote starter. Can't live without it in Chicago winter!) I can change oil without jacking the car up now and it literally takes minutes to change oil. Had it on since the car was new (almost 3 years) and no problem whatsoever.