If your engine would start and with your foot on the pedal could run half decently even if it's at higher revs then it is not likely the AMM. A bad AMM generally means very poor running or a complete no-start. Disconnecting the AMM puts the ECU in "limp home" mode. For a no-start or extremely poor running, if disconnecting the AMM now allows starting or if running improves then it is the AMM, but that doesn't sound like your case. Go back to your original AMM for now as it was at least known to be working. You do not need to disconnect the battery to change the AMM. Just having the ignition off (not KP-II) is more than sufficient, even with the ignition on there's minimal chance of causing fatal damage, but it's still not a good idea. As for getting a new AMM for $35, well how do I politely says this, likely it's of very inferior quality and you'll be lucky if it even starts the engine, let alone runs it half properly. At best I'd consider it a spare. At worst it's a desk paperweight.

As for your racing engine and stall when you take your foot off the gas, it strikes me the ECU either has no idea it's supposed to be maintaining idle or it is totally unable to control idle when it tries to. For the former, think about a possible bad or disconnected TPS or a really dirty throttle plate area in the throttle body throat that doesn't allow the TPS to close. For the latter, think about a bad or possible disconnected IAC valve. My thoughts are leaning toward a bad IAC at the moment. Start by checking those areas. Good luck.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now