Well my '92 245 has been running so nicely I haven't been here in a while. But a couple of days ago, it just lost a lot of its power. Definitely not the "limp-home" level of power loss characteristic of a bad AMM, but real leisuely acceleration. Idle is fairly normal. It will rev all the way up to redline (at least in the lower gears), but it takes forever to get there. Recent ignition tune, less than 3K ago. So far I've checked the inlet for obstructions (none), plugs look normal, cap & rotor look new, wires are new. The tank is full so I know it's not the fuel line on the in-tank pump; swapped in a known good FP relay, and checked both pump fuses. Neither pump has changed its sound level. The car has about 175K on it and it's the original cat; I've considered that it might be a plugged cat but the revving to redline in low gear sort of rules that out. No obvious vacuum leaks, and there's a new FP regulator as well. The t-belt is close to 50K, but has been regularly tensioned. Overall, the engine just feels like its ignition timing is way off. The one thing which does seem abnormal is that the throttle position switch does NOT click.

So - what am I overlooking? No 'check engine' light, so I haven't checked for codes. Any suggestions?

I'm less familiar with the ignition controller on your '92, but it sounds to me like it's operating in 'default' mode, a very mild advance curve. This could be because there is a lack of some ignition signal (like vacuum or knock sensor), but it seems like that would probably light the CEL.

The cat is also a prime suspect. Sometimes a chunk can fracture and reorient itself so that it blocks the flow, essentially choking the motor.
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Speed Racer, '83 240 R, '74 164 E, '93 940 OL1 (Manchester, CT)

"... a plugged cat but the revving to redline in low gear sort of rules that out..."

Not really. And a plugged (or plugging) cat would be on my list, although 175k is a bit early. As the cat begins to obstruct the exhaust, it first affects high speed at heavy throttle. You can get to red line in lower gears because it doesn't require full throttle, while red line at highway speed does require heavy throttle -- and therefore has much more exhaust flow, which gets blocked by the cat.

A plugging fuel filter can have similar symptoms.

If you had a significant problem with the engine management system, you'd get the "check engine" light and error codes.
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Don Foster (near Cape Cod, MA)

Well, this morning on the way to work the car did lose nearly all power... definitely "limp home" mode. No difference with the AMM pugged in or not, so that's my principal suspect. Swapped in a fresh fuel filter, and that made no difference. Having suffered a failed cat on my previous 245, I really doubt that as a player... there's been no gradual deterioration in power at speed, and no rattles of any sort to suggest internal structural failure. Looking for a good AMM to try... probably will have to buy one.