IDK. Is it a surge out of the blue? Or is it a decrease first and THEN catches up? How often? There's a lot of components & subsystems that could cause a surge. Besides a torque converter.
I'd start by wiggling & reseating engine sensor (and tranny) and engine bay harness connectors. Just the tranny has numerous pins in it's connector. Make sure the throttle body is very clean (oft overlooked). Make sure air path is not leaking or obstructed. Intake sensors clean. PCV is working and hose all good. Wires haven't been rodent-chewed, No vacuum or intake leaks, etc. Inspect coils for cracks/electrical traces, ohm out..connectors good, plugs good. VVT solenoid isn't plugged, gummed-up, sticky, etc. Tranny filter/s replace (again if need be) and no loose valve body bolts. Swap out shift solenoid/s etc.
First a guy has to rule out the 'basics'. Start with PCV, vacuum & clean throttle body. Throttle position sensors can flake out. Coils can become flaky or cracked. Those alone are common sources of problems which can cause more other symptoms than people think. Unfortunately there are a lot of 'basics' these days on cars/trucks. If a guy could put a scanner on it and do a freeze-frame 'look-back' when it occurs, that might reveal something.
