Stock, an 88-89 had 206hp at only 10psi of boost. It doesn't take a lot of tweaking to get 250+ hp. That was with a small 12a turbo. I bet the 14 dealer installed upgrade made 250. That's with a long stroke 2v motor with lousy breating off a simge barrel TBI setup double wye manifold with really crappy distribution.

The 4g64T with a 4v head and much better IR + plenum intake will make nearly 250 at the crank. The original 4G63T made 198 at the crank. With a 16 size turbo for a lot more air, I bet you will have 300+. with supporting mods, 400 is easliy possible.

I think 300ish is all the tranny will reliably handle, but add cooling. You also will need oil cooling, and I think you need a three row radiator core installed. I only overheated my 2.6T once on a three row. I was climibing Bear Mountain Pass going to Lake Burton south shore on a 90* day. It's a steep pull on a long ago maintained FS road, and with all the turbo low end torque I could lug it up the grade creeping across the washboard at about 4ish mph without downshift, with very low air flow thru the radiator and very low water pump volume due to low rpm. The temp creeped up slowly, and when I downshifted into lo range, the problem went away. The tranny makes a tremendous amount of heat at low rpms since the stall is at 24-2600 rpm, and you need sub 200* water in the bottom tank water/oil cooler to suck it up, especially when the hot ambient makes the secondary air/oil cooler less effective. The tranny is durable, but you could heat a house with it.