I don't know about MR2's, but at least with the 7m-ge vs 7m-gte (MK3 Supra), there are several differences between the 2. It is possible to turbo the N/A, but it's almost worth just to get the turbo engine (I lucked out and have the turbo Supra lol)
if you were to turbo the N/A engine, you'd have to a piggyback system for the ecu as well as upgrade the injectors, fuel pump, modify the exhaust and more work, not to mention adding in the Intercooler and plumbing for it. I'd almost say its just worth buying the 3s-gte.
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1988 Supra Turbo- Stock 7M-GTE, 5-speed manual, HKS Turbo timer, ARP headstuds, planning 2jz-gte swap
1988 MR2- Stock 4a-ge, 5-speed manual, planning 20v swap
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