Right now i dont have much done to my XI beside a QTP 3in downpipe with cutout to stock exhaust, intake and manual boost controller.

I am looking at getting the cosworth 272 cams with dual springs, TI retainers, Spring seats and viton coated valve seals.

I was wondering if i could pull off keeping my stock exhaust with cats on and have it tuned with the downpipe open for max power. Would it affect the engine, besides loss of power, when i have the cutout closed and im at WOT such as detonation or anything like that?

Also does anyone recommend getting injectors and a fuel pump if im not planning on upping the boost over stock or getting a larger turbo?

thanks