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This isn't a matter of the wrong size pipe, or the "wrong" throttle body. Unlike Roots superchargers, stationary turbochargers do not pose a restriction to an idling engine, and they should never be bypassed, nor should you build a purposefully restrictive exhaust system upstream of a turbo for any reason. 1.75" pipe is far too small. It is smaller than Toyota used on any part of the naturally aspirated exhaust system! You may need to neck down to that size at the turbocharger, but running any length of small tubing like that will choke your engine at any power level, create some serious heat, and potentially fatigue the parts to the point of failure prematurely.
Air is air when we are talking about low load, low speed conditions like this. At this point you need to determine whether the problem is one of plumbing (physical blockage, air or vacuum leak, etc) or one of management (TPS not communicating properly with ECU, defect in the wiring, etc).
Are you using the NA throttle position sensor with the SC computer? If the ECU isn't getting the information it needs from the TPS, it will not recognize what the throttle is really doing, and will not manage the engine correctly. It could issue the wrong spark timing, causing the engine not to rev, or it could even shut the injectors off outright if it thinks the throttle is closed and expects the engine to be idling.
One more thing to consider: is your knock sensor present, functional, and connected properly? Knock sensor failure or absence on a 4AGZE puts the engine into "safe mode" where it effectively won't rev at all, even under no load. This plagued a friend's GZE swap until we popped in the smallport knock sensor I had laying around, and now it runs perfectly. That one little detail made all the difference between a functional car and a useless moaning pig.
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