Running GREAT and then rough…..hhhhmmmm, engine runs rough at one place in the power band Options

[ctc911ctc]

-Update -

I removed the TPS, calibrated it as per instructions on the Bird. Here are some pictures.
I would like to be able to "RING" this out, not sure what I would be looking for. Though we know that one course is to install a new board and then calibrate. There is little else I could find to assure operation. Any experience with asserting these things are good.

Some pics



Any ideas would be great!

-End of Update-


I am a bit befuddled as to which way to go so I decided that the 914W team would like to hear about this puzzle.

Background
'74 2.0, garaged from '84 until 2018, 22K miles
Running since June.
Repaired or replaced:
Entire Fuel System - tank, lines, injectors, pump, pressure reg
Adjusted the valves
Removed and rang-out the engine harness,
Rebuilt the MPS
Rebuilt the Plenum and tested it for leaks - none observed
New gaskets at the plenum and manifold at the engine
Rebuilt Throttle Body, very minor leaks around the actuator (throttle), New circuit card
New Plugs, points, cap and inspected the distributor for all of the regular ailments - super tight.

Engine idles great, pulls like a monster - sounds like a German symphony

HOWEVER
Last night I drove it back from the paint shop on 93 heading south from NH to Boston (lots of beeps from newer Porsches (IMG:style_emoticons/default/smile.gif) (IMG:style_emoticons/default/wink.gif) ) and found that the car started to buck and the engine runs rough when just a small amount of throttle is applied.

More Detail

If you are doing 55 and want to maintain that speed, it is necessary to apply a small amount of gas to sustain the speed. This is when the cars starts to exhibit this "miss/run-rough" puzzle. If more throttle is applied the bucking stops, the engine is smooth and all is well. Conversely, while de-accelerating there is no bucking.

This problem is NOT velocity-dependent, sustaining at 30/40/50/60 will exhibit the same reaction.


WHERE WOULD YOU START TO LOOK IF YOU HAD THIS CHALLENGE?