Greetings, wise folks!

I've been trying to puzzle through the problems which cropped up about a month ago on my K-jet equipped '81 B21 with 190k miles. Here are the symptoms:

Intial startup is quick and smooth. After about 15 seconds, it gets *really* lumpy, and takeoff bogs down and missing is frequent, particularly at low rpm and heavy applications of throttle. When the car gets warmed up, idle is only mildly lumpy, and takeoff is satisfactory with no missing unless I hit it with a heavy throttle. Going up grades warmed up, the engine misses at low rpm. Downshifting into the 3000+ rpm helps a lot to smooth things out.

I was initially suspicious of a significant vacuum leak. I'm not sure that's the problem -- the intake manifold gasket is only 36 months old, and the bolts are down tight. I've isolated the charcoal canister and the interior heater control vacuum lines, with no change. All other vacuum lines are fresh and tight. The injectors, injector holders and o-rings are only 18 months old. I've sprayed all around the engine with propane and carb cleaner on multiple occasions (I had the injector holders 'swimming' in carb cleaner) with no effect. The big rubber bellows from the distributor to the intake manifold is on tight.

In the elctrics department, the spark plugs are 6 months old, cables are 6 months old; I've sprayed them and the harness down with water mist and I see no sparking. The coil is 36 months old, the engine harness I rebuilt 36 months ago. I resoldered the fuel pump relay circuit board 4 weeks ago. The control pressure regulator (warm up regulator) was rebuilt 3 weeks ago. I replaced the oxygen sensor 3 weeks ago. On the suggestion of a colleague that the temp. sensor for the fifth injector may be malfunctioning and the injector is spraying all the time, I unplugged the injector, and there's no change in engine performance.

Last summer, my '83 LH-jet equipped B23 displayed similar symptoms for several days before its Hall effect sensor pickup died. Might the reluctor coil in the distributor of my K-jet be similarly ready to give up the ghost?

I'm stumped and am about ready to take it to a $$$ Bosch specialist. Any last suggestions on where to turn next before I take that plunge?

Thanks a million in advance.

Rob