Ok, so I need some opinions here on what to do. I have an 04 D23 with the Fswerks 2.5" race exhaust and K&N Typhoon CAI with no tune. I have two options on what I can do next because i'm on a very tight budget. My first option is getting an aftermarket header and flex but the problem is that I'll need to run a high flow cat (dont ask) and this will be with a tune. My second option is getting some stage 1 cams with a tune. Now i have two questions, would the cams and tune not be worth it with the stock exhaust manifold? and how much of a loose am I going to see with using a high flow cat vs going catless?