Series 4 NA Throttle body on a series 5 NA?
 

Having an idling issue on my 90' S5 which I discovered is being caused by a missing chunk from my throttle body. I've searched all over for what it might be called, but it's a screw/bolt resting atop of what appears to be the throttle. The screw that's there currently is a very weak temporary fix that holds it idling at around 1300, but with any large pothole or bump the screw comes undone and jumps the idle to 2500 or doesn't let it idle and chokes out. I have a series 4 throttle body sitting around, and I was wondering if I would be able to replace the old tb with that one, or if I specifically need an S5 tb. Ask me any extra info I might have left out

The s4 throttle body uses an S4 TPS...so it won't work.