88' 300CE, more throttle input, less go??

[PMMJKL]

Hey Everyone!

So I've got a strange problem on my hands. The car in question is an 88 300CE M103 powered, factory four speed autotragic, 172K miles.

It's been doing this thing where you give it the beans, and it refuses to move. It's a inverse relationship between throttle input and actual movement of the car. I'd say it will drive normally-ish until you give it about 50 percent throttle/WOT. If you do give it more throttle, it just feels like all the power just disappears and doesn't do anything. Sometimes if you modulate the throttle you can get it to shift, but normally it'll just sputter or hang in the midst of attempting to shift, or just not do anything.

Car has no check engine codes, recent top up of fluids, new OVP relay, newer alternator with voltage regulator (used for 10K miles).

Initially I had a problem like this with the car where whenever it rained it would do this until it was fully warm. Replacing the alternator and voltage regulator, as well as just kinda of randomly cleaning up sensors on the engine seemed to resolve it.

Now the problem is back, and despite the newer alternator and now the new OVP, it continues. What's strange is that when I disconnect and re-connect the battery it drives beautifully (im assuming this resets the ecu with Mercs), it drives brand new, until it gets warm. Sort of the converse of the initial problem as that only occurred when it was cold/raining.

Now the problem becomes full blown when warmed up. At first I thought my trans was crapping out because the problem in person seems like the trans is just going ( and it is showing signs of age, delay going into reverse, clunky shifting, etc). But after ECU reset, the problem is non-existent until it starts to get warm and you start giving it some throttle.

So, any ideas? Throttle position sensor/fueling or something like that? I'm not very familiar with K-Jet equipped cars, and before digging into that rats nest I wanted to see if this sounded familiar to anyone. Any help or pointing in the right direction would be incredibly helpful as she's my daily for the time being. Thank you!