My RS has a 2.8L MPFI V6, and she's been running pretty rough since I got it (a few weeks ago). It has brand new plug wires, distributor cap, and rotor from Accel, and a MSD coil. Also, the EGR and Charcoal Canister have been removed.

Basically what happens is I start it up and for the first couple minutes I have to feater the throttle to keep her running. Then when it will idle on it's own, the idle jumps around a lot. It will start out around 2K RPM and sound alright, then it will drop to about 1K RPM, start to sound like crap, and try to die out. Other times it will go all the way to 4K+ RPM and stay there for a while. Then when I'm driving it, it can sometimes be hard to hold a steady RPM unless I really give it some gas. Another thing that will happen is when I let off of the gas it will stay at whatever RPM it was at for a second or two (which is not so great when shifting).

I have a handful of ideas as to what it could be, but I'd like to get some outside advise before I start replacing a bunch of stuff.

I would inspect your vaccum tubes for leaks. Check to make sure that there are no cracks or open tubes. I would also get some MAF cleaner and clean your MAF.

Definitely check ALL vacuum lines! This is a very likely suspect...

Also take out your IAC and clean and test it as well.

Sounds like a pretty decent size vacuum leak to me.

Sounds like a very sticky Idle Air Control valve, combined with a bad/off Throttle Position Sensor. Pull the IAC from the throttle body, clean it out with some solvent, then inspect your TPS. The TPS might still be good though, but it's setting could be way off (possibly because of the former owner)....

How do you set the TPS? I'm thinking mine mught need to be changed and adjusted soon.

How do you set the TPS? I'm thinking mine mught need to be changed and adjusted soon.

You will need a digital voltmeter to set it. You have to get the reading and set it within certain specs. I can't recall the specs though.

We ran the codes on it today, and got a Code 15 which is the ECT Sensor according the book I have. Is it possible that that is causing some of my problems?

Aside from that, I pulled the IAC and it was pretty dirty. I sprayed it down with some Throttle Body Cleaner, but it didn't seem to help much. I think I'm going to see what I can to about the TPS next, as I'm pretty sure its set wrong.

I replaced the ECT sensor today and it runs/drives better, but the idle is still off a bit. I guess I'll move onto the TPS next, will a Haynes manual tell me how to check/replace it?

Yes it will, it will also tell you how to adjust your idle the right way.