Engine runs but sputters when put in gear

You'll need to change the distributor, as the distributor shaft oil seal has gone bad. Without sufficient spark, you'll have no power. Don't forget a new cap/rotor.

Throttle position switch could be the problem

Hi
Yes, its the typical indication of turbo gone.

the ECU is messed up or the Throttle body is clogged.

Sounds like a fuel pressure problem, either the pump or the filter among other things.

Turbo is not boosting

That vehicle never came with a turbo as an option. Therefore adding a turbo would be custom work. You may find someone online who has documented their modification process. If you purchase an aftermarket turbo system it will come with a manual. Short of that such a document does not exist.

is the turbo working? if fitted! the standard turbo is not too reliable, also get a good tune up,problem may be fuel related.

Sounds to me like you have a leak somewhere in the intake system. The idle fluctuation sounds like a vacuum leak- and of course, when the turbo spools up, you have positive pressure replacing vacuum. Look for a loose hose clamp or a torn hose, etc. etc. By the sounds of it, you shouldn't have any trouble finding the leak.

Nissan Scope Certified Technician- 10 + years experience in Nissan dealership

that maybe what the rev limiter is set for.That way you can not over rev causing engine damage.