I have one, and expected it to be a totall piece of shit, and went through the whole thing with a porting bit and took alot out of the runners. then smoothed out the runners with the smoother sand paper bits. then bead blasted the whole thing. Then, I assembled the throttle body, I looked inside to see if there were any restrictions, and found a fairly decent amount of material I had to remove to get the STOCK throttle body to match up! after that I took a tap kit and retapped all of the treads. Some were good and the majority were horrible i.e. idle air control cracked on the corner, throttle body threads were horrible. after I got everything bolted up and port matched the head and made my own gasket, it seemed to respond faster when revving. I do have a bigger turbo and larger injectors, Z32 and the like. So its up to you. the whole process took about 4.5 hours. the casting is garbage but with a little work you can make it worth it. I don't have any hard numbers but you can definitly feel the difference.