Will not rev past 3500 RPM

Looking at what little information the service manual shows I would start with testing the TPS and the APS to see if they are in range and the intake air and coolant temperature sensors. From the information those seem to bee the controlling items for the limiter. This is assuming a stock engine with OEM tuning.

If the ECU is shutting down it is not the limiter, it only cut the fuel by stuttering the relay to the pump not killing the ECU.
Does it shut it off regardless of how fast you apply throttle? And how does it recover? When the rpm's drop does it start running again or is it up to 3500 and off until you restart?

What does the battery voltage off the alternator show as it shuts off?

Well that isn't something you see every day !
I'm going to dig through the book, at the moment the only thing I can think of is something strange like a cracked part that centrifugal force is moving and killing the voltage to the ECU.
How about sticking a VOM on the power and grounds to the ECU and see if the power is dropping out at the ECU. That would at least give a starting point. Then it would be unplugging sensors and seeing what happens.
You could try an odd test, pull the drive belt off the front and see if it revs then. That would at least eliminate those items from being a problem.

Have you had any luck on your end finding the problem? I've gone through the book and there isn't much in there. The one thing that I did see was related to the limiter. It is supposed to activate at 7000 rpm on a cold engine. You are having this issue at 1/2 that speed. Makes me wonder if the signal for that isn't something to do with the problem but the book doesn't really talk about that, only that it's part of the ECU.

Great to hear. Gotta love how companies hide info at times.
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