Having worked on and driven both the OEM GM TBI and long runner MPFI 250 I6 engines, find a later MPFI intake for a 4.0L and swap to MPFI. The TBI is a good system, but it still has the same issues prevelant to a carburetor that are especially troublesome on the long I6 intake runners. The 2 center cylinders end up running rich and the 4 end cylinders end up running leaner. With an unheated air intake and unheated divoriced manifold the a/f split becomes even worse at idle and lower loads. The port fuel will run smoother, get better fuel mileage and have better driveability especially after a cold start. You can still go the GM management route to make things easier to tune using the later 4.0L MPFI manifold. I say later model 4.0L manifold because somewhere around 2000, Mopar redesigned that manifold to flow better to offset power loss from other changes to clean up emissions. The older 4.0L manifolds have a long straight plenum and straight runners, where the better manifold has long, curved sweeping runners that branch out from under the throttle body. I would use the 7730 ECM to control the system using a speed density 1990-1992 3.1L V6 Camaro or similar calibration. It would also be worthwhile to integrate GMs 7-pin EST module to the OE Mopar distributors pickup setup, delete and lock out the mechanical and vacuum advance mechanisms, and comperize the ignition timing. I have integrated that TBI/TPI style 7-pin module to both Mopar and Duraspark style distributors, ditching the failure prone control modules and vacuum/mechanical advance setups on both. Hardest part of that is setting up the latency table, but even that is straight forward using a timing light and fixed timing values of say 15-20* in the spark MAP. Fix the timing values to where they are all the same, then adjust the latency at various RPMs to make the ignition timing match the commanded value. End of the day, TBI is an improvement over a carb on an I6, but if I am already doing major surgery, I would want MPFI, especially since a low cost MPFI manifold, fueql rails, and throttle body already exist for that type of engine at just about any local wrecking yard