theres been a lot of debate about these... flex: pros: flex section allows for some amount of independant motion at both ends... lower probability of breaking/cracking... easier fitment cons: some say that flow isnt as smooth solid: pros: some say flows better cons: being solid, it has no ablity to flex, hence greater chance of cracking/breaking... fitment may be more difficult my experience: i have always gone with flex uppipes... also i have never heard of a flex uppipe breaking whereas i have seen 3 solid uppipes broken at the flange
people have been happy with the gutted stockers... however i am not sure how good the flow will be since the inner diameter varies dramatically... however i doubt it will make much of a difference for a setup using a stock turbo... also its definitely cheaper to gut your stocker than buy another... plus the stocker flexes i had the PDE on my WRX and i liked it a lot... it has an accordian style flex section but if u look inside it, its sleeved and theres just ~1mm gap between the pipes on the 2 sides of the gap... i havent looked inside other aftermarket flex uppipes so i cant compare but it definitely looked smoother than a gutted stocker
peopel have dyned stock gutted vs HIGH end and have seen virtually no diff, in some cases the stock did better due to the thermal sheilding
My personal opinion: I prefer solid, and have no concerns about it cracking as long as the install is done properly. Have had a Perrin on for something like 14k miles without issues.
No difference. Buy whatever is less money and use it. I have a solid HKS that has worked fine for over 2 years now. Use the correct torque specs and gaskets, there should be no problem.
I've seen 10 broken, cracked, or leaking solids. I've never seen a SINGLE problem with a properly installed flex... SS