I'm needing some help on this one....I want to add a new downpipe and cat-delete on my truck. Right now it's got a 4" MBPR cat-back system on it, intake, intake manifold, and programmer. My questions are:
What is the size of the stock downpipe?
Will adding a 4" one help or hurt the enginge, power, & mpg?
Will deleting the cat help or hurt the enging, power, & mpg?
Will this cause the engine & EGT's to go up, down, or stay the same?
Will this have any effect on the tranny and it's operation or temp?
Any chance this will cause it to run rough or make the check engine light come on?

Thanks for your time. Feel free to offer any other advice about this thread if you have any.