This is a simple question that yields a complex answer.

20hp to 100hp sounds reasonable.

 

Like richiethomson said, it gets complex. It all depends on if you are going with a factory setup or not. If you are building your own turbo engine, the expected horsepower depends on engine modifications and the model of turbo you use, which can lead to a completely custom engine management problem.

Factory, for the 1987 model year:

The factory 22R-E was rated at 116 HP.

The factory turbo 22R-TE was rated at 135 HP.

That gives you about a 19-20 HP increase from the factory.

 

I1987 RET TURBO 4 RUNNER
I figure the upgrade to the ct26 + 2 1/2" downpipe and exhaust no cat + 82 supra AFM at 10 lbs boost is close to 180 hp ... we'll see when I dyno it and sniffer it for AFRs
I know for a fact, it's awesome and fast when in power mode after about 1800 rpm you better be ready to roll... I held my own for about a block with a dodge challenger last week... and backed off...i didn't want a ticket... my wife would take my keys away
If I had been in that car, I would have chased myself down and asked... What the heck is in that thing?
seriously it's stupid quick for a 4 runner...
i'm looking forward to doing a road trip to Arkansas to do some mountain trails...
I'm 64 and I'm not into tearing my stuff up and I've spent about 6 years getting this thing running like i want it... very happy with the results...