crazy03gt

I have an 03 gt and am looking at throttle bodies. All I have done to the engine is a JLT CAI, and IM wondering if I should go with 70mm or 75mm throttle body, it says on the site that this setup is only suggested for pretty heavily modified GTs as a stock and mildly modified GT does not flow enough to benefit from the larger Throttle Body, andIwant to knowifI have to upgrade my MAF sensor.

03GTVert

You don't have to upgrade the MAF, but upgrading the throttle body on an otherwise stock mustang isn't likely going to get you much if any HP increase.