The stock twins do spool up fast, but only because 1) they're small and 2) because they operate sequentially. Read more about it here:
http://www.mkiv.com/specifications/ncf/ncf93/ncf088.jpg
http://www.mkiv.com/specifications/ncf/ncf93/ncf089.jpg
http://www.mkiv.com/specifications/ncf/ncf93/ncf086.jpg
etc...
No, the stock twins can't produce 700rwhp. Whomever told you that is 'smoking crack'. If you're talking about aftermarket twins that run in parallel, then sure 800rwhp+ is no problem, but it'll lag just like a big 800rwhp+ single turbo.
The oem Mkiv Turbo is electronically limited to 155mph. With a US-spec Mkiv Supra Turbo, removing that electronic limitation is as easy as pulling the trac fuse.
Bikes are about as aerodynamic as a brick at 150mph+. You'll find an upgraded Supra exceeding that easily because of the much lower drag coefficient.Depends, but I'd say about 525rwhp reliably. There are upgrades available that will take you to about 675rwhp with the oem TT auto, but to go past that you'll need to swap it out for a TH400 or the like.An AEM ems works fine with ODBI. With ODBII it's a bit trickier - I've heard of some folks leaving the oem ecu in there for emissions, and using the AEM to control the engine.
Everything you saw in that wikipedia article is accurate.Sure. Either that, or you can inject it separately. Your choice.Depends how much boost you want to run.um, because that's what you need to do to increase the peak hp at higher rpms? The information we've accumulated over the years in this community is thanks to dozens of early pioneers that experimented with the Mkiv Supra Turbo in the mid '90s. Lots of things were tried, and only some worked. The ones that worked were published so it's easy for the rest of us to take advantage of. Again, here's the link:
http://www.mkiv.com/techarticles/cam_gear/install/index.htmlNo, only the fuel system.No, again it depends on boost. More boost, more octane. Forget hp.
I'd guess about 350rwhp max through a 6spd. Possibly 325rwhp-ish through an auto.
Do you mean stock (sequential) twins, or aftermarket parallel twins?

For a '94, 89K miles is LOW. I've seen more than one well-maintained Mkiv Supra Turbo go single-turbo at higher mileage than that, and put out 700rwhp reliably with no issues whatsoever.

That car won't be around long. If it's still available, put cash (not a check!) in a briefcase, get on a plane, and buy it if it checks out. You may already be far too late if it's legit.

Oh, and a hard-top is more desireable: it's more rare, and as you said the lower curb weight makes it a better (GT) sportscar.

Best case, find a local Mkiv Supra Turbo owner that can take it for a test-drive. That way, you'll have an objective, well-informed opinion about the performance, handling, and all of the specific the sounds it makes during the test drive (turbos, transmission, etc.). If possible, find a local shop with extensive Mkiv Supra Turbo experience, and pay them to give it a complete once-over. At the very least, pay your choice of a local Toyota dealership to check it out. It's critical that you get an qualified, objective third party to provide input.