i also was wondering ,i have an egr on my truck and a cat un my 4 inch exhaust,how much does this hurt my performance

 

Performance really doesnt matter untill you are able to get the power to the ground. Untill your factory TC locks up all the power you might have is just generating heat thru fluid shear in the TC. The emissions stuff does not help performance as you can imagine. However it is not appropriate to remove those items.