Had my kit on for about 6 months before deciding to sell the car No problems with it during that time.
Only thing I would do differently is to have gone TT instead, initial outlay was a similar cost & in hindsight I should have gone that route. I love my car with the HKS kit fitted, but I prefer the kick of a turbo
If you do decide on the HKS kit then avoid GTM, I had loads of trouble with them ignoring emails & phone calls after I had paid for my kit