Spool up was fine when I was running the stock exhaust elbow but I had to install a larger wastegate puck because of the size of the hole in the turbine housing. I was also running a kirban 3 in dp and stock exhaust, dump pipe no cat. converter. That was my concern when buying this turbo. I asked the person I bought it from and he said the same thing but I did check into it. This turbo could come with two different turbine housing .63 or .82 ( do not quote me on the exact ration but I know they are close, anyhow) this turbo has the .63 turbine housing. A couple of weeks ago I installed the 3.5 dp and RJC 3 in. exhaust and did some other work now the spool up isn't as good. I just have not taking the time to find out why yet. Something else I just thought about, when installing the 3.5 dp the threads in one of the holes the dp bolts to was ugly so I helicoiled it while I had it apart. Let me know if you have any other questions.