Ok, well I've just about all of that except for steps 6 and 7 which I'll check soon, but I doubt they are the problem.

I've replaced all of the vacuum hoses coming off of the manifold except for the one for the boost gauge. I also checked all of the boost hoses and replaced 2 of them.

Last night I replaced the ECT sensor for the FI (the one toward the back of the engine) and tested a brand-new TPS sensor. With both the old and the new TPS sensor the car acted the same, and no difference was noticed with the new ECT.

What the car is doing is reving up to 2k RPM in park/neutral and bouncing off of the idle rev gaurd. This drops the idle a few hundred RPM which immediately climbs back up. The car is now "cycling" the idle every few seconds and it sounds really bad. The car has no idle dip when sitting in drive with the brakes on, and idles about 1400RPM steady.

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Background on why the TB idle stop needed to be adjusted. I bought this car about 3 years ago, and after a while it began idling rough at around 800RPM. My mechanic at the time just adjusted the screw so that the car would idle higher. He never messed with the TPS or anything else because he's not familiar with Volvos. Well any time the car would have problems idling, he would just adjust it higher until it was just nearly 1500RPM in park. I sold the car about a year ago, but I aggreed to help them work on it last week. When I cleaned the TB, I adjusted the screw back down thinking it would help lower the idle, now that it's got a new ignition system which it's never had since when I first bought it. Well to my horror, now the car just idles higher. It clearly is getting better spark as the performance has never been better, but the idle is now bouncing off of the 2k limit.
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Any more ideas? I'm thinking of replacing the IAC next, but hate to spend that much for something I'm not sure is the problem. I have searched much of the FAQ and nothing sounds exactly like this.