My own P220 is not quite as tricked out as your amazon. I also have a crane ignition, but I have a stock B18, with one previous rebuild, I have dual stock SU HS6s in pretty good condition. I also have a stock cast combined manifold w/o carb spacers.

Mine generally idles okay - never dies at stop lights or anything like that. Although when the idle is down to 800 I find that it doesn't start out very nice from full stops. It requires me to rev it up quite a bit to avoid stalling it out. When the car reaches full temp it will not idle lower than 1000 rpms, either just coming off the highway, or sitting and running in my carport. I think it is definitely a heat-related issue.

I imagine that you still have your heatshield installed? I just pulled and replaced my busted manifold and took the opportunity to clean and re-paint my shield. The original owner aparrently considered this heat transfer troublesome when livign in Texas. He wrapped the sheild with insulation and followed that with an aluminum foil wrap. I guess it worked for it's intended need. It's not so hot up here in St. Louis, so I removed it (I have a different plan). The original owner had 38 years of experience with the car, so I think that he may have been on to something with the extra heat sheilding.

I plan to take a different route, and will be wrapping the exhaust with 1 1/2" fiberglass tape ($30 USD - check at a performance/speed shop). This supposed to keep the exhaust at a steady temp, allowing the exhaust gasses to get out faster and to allow the cylinders to push the exhaust out with less force leading to better fuel economy.

The heat/rust/noise in VWs web-article covers this in a little more depth.
http://www.shagadelic.org/VW/info/gmbulley-soundproof/intrir1.html

This might solve your problem. I have not wraped by mainfold yet due to other mechanical problems that I've been chasing.

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1967 P220 Amazon, 1972 145S, 1976 245 DL, 1983 245 DL, 1986 745 GLE, 1990 745 GL, 1995 945....
You mean to tell me that Volvo makes cars that are *NOT* Wagons?!?