Your car is a 90 M47 car right? I think 3.1 started in 91 manual 240 NAs, but it is possible that your 90 has it. Anyway, the flywheel for my car came out of a 91 240 NA LH3.1 I am almost positive, and it works just the same as the OEM turbo LH2.4 flywheel. I also think the connectors and pinouts to the ECU for 2.4 and 3.1 are pretty much the same. This means that you ought to be able to swap to the LH2.4 turbo ECU, AMM (hot wire for 2.4 instead of film type for 3.1), and LH2.4 TPS +greentop injectors and resistors. There wll be some veriations on this theme if the LH2.4 ECU has the cold start or EGR stuff, and whether your 3.1 ECU is designed to deal with that stuff, but it seems worth a try to atleast try and plug in any 2.4 ECU + 2.4 hardware and see where the pinouts lead and what it does. Or, you could just not bother messing with LH2.4 stuff. THe 3.1 seems like it was more sophisticated, being that it had a switched and variable resistor TPS if I remember right. That is a setup much more akin to the hardware you find on the motronic stuff in 850s than 740Ts per se. 3.1 turbo would be a cool experiment, though I am really not sure how heavily 3.1 leans on the TPS reading. I know it must lean on it some because the film type AMM responds slower, but I am not really sure if you would drive normally or badly with a turbo. It could be cool to see where it leans out to maybe run a piggyback on your NA 3.1 system.