I just put a Diablo sport tune chip in my car last night. I noticed the shift points are much firmer and the throttle response is faster but how much horsepower gain am I realistically looking at. I have flowmaster exhaust and am putting on a K&N intake setup later this week.
they say about 10%-15%, so I would say if you have 250hp you get a max of 25 hp, it will most likely be lower than that, but it could be anywhere from 5-30hp depending on the tune