Another Fox-specific Technical Question...

[1andonlywhitie]

Alright, needing a little diagnosis help from other Fox owners...

Driving around and engine braking the car makes huge vacuum and overall runs great but at idle it's rough, stumbles and just generally runs like shit. The vacuum will sit around 15-16 and as it stumbles drops to around 10, it'll catch itself and the nasty idle continues. Now I've looked over vacuum lines and they all look good, I have a few of them capped off so it doesn't take much to check them. IAC looks clean, MAF was inspected a couple thousand miles ago but may be due for cleaning, fresh plugs/wires a couple thousand miles ago.

My plan is to buy a new cap/rotor and see if it's ignition related (the car sat for ages before I got it and the contacts inside the cap are a little burnt) but I don't really have the money to be throwing parts at something. Is there generally something on a Fox that causes this or am I just gonna have to dig into it? Does the EGR valve if it's bad cause a vacuum leak at idle that may cause these symptoms? Any suggestions would be great!