Tough for me to answer this question. It has been over 4 years since I ran a stock 7900. Back then I compared the 7900 to a 460 but felt better mainly due to the anti vibe I guess. This one only had 140psi when I got it so it needed help in my opinion. I have never checked compression since the build but I guess I could.How much improvement over stock????
Is it better than stock yes, how much better is hard to answer. If I wasn't milling my 660 would find a new home.