I had a hard time tuning my 4g37 thats fuel injected when i went turbo. Took me a while to figure it out. But after hooking up to the stock ecu and logging it i found out the ecu has a maf cap and injector duty cap. The ecu ignored everything over around 800hz. My safc would show max hz readings of around 1800-2400hz . Also no matter what i did injector duty never went much passed 50%. And then i saw that my timing was around 33 degrees advanced during wot. Also the ecu staying in closed loop even when in full boost, if it was under 4krpm. So if the ecu on your 64 is anything like a 37, it sucks a big one.