If you want to use a larger throttle body than our 59mm unit, you'll need to port the upper intake to see any more gain, because the stock port size is 58mm. For those customers who only want an upper intake manifold, we offer this part by itself for a very affordable price. All of these intakes have the throttle body inlet ported to 65mm to accomodate aftermarket throttle bodies, All 3500 intakes get ported to 68mm. You can choose to only port the throttle body inlet, or do our full port job. If you choose full port job, this is the same upper intake we include with our ported upper and lower intakes.