[carnut]

I think the biggest clue is the blanking out of the displays. I would suspect either the climate control head or the mileage display head as faulty. I.E. loosing the ground signal. On this early computer system, I've never found it necc nor have I seen an issue with it relearning parameters after an ECM disconnect, unlike my later 91 Allante which requires a structured idle learn procedure. I think it would be a good idea to drive this vehicle with the fuel pressure gauge positioned to be able to confirm steady pressure when this surge, stumble occurs. One other thing, check and adjust the TV cable at the throttle body to the trans. Early upshifts cause cause a surge to be felt. You can monitor torque converter lock up thru the orange dots in the climate display as driven as well. Is it locking up too early??