Engine won't rev

I just rebuilt an LT1 for my 94 and the engine starts fine but won't rev past 500rpm. There are no codes. I thought it might be a plugged cat so I dropped the y pipe. No change. Put my scanner on it and the computer is requesting 800rpm but not getting there. It will eventually get to closed loop but still wont rev. Any ideas?

double check the timing and look for vaccum leaks.

You know, I pondered this one for a while yesterday when I saw it. Is the PCM seeing the throttle position (change)?

You know, I pondered this one for a while yesterday when I saw it. Is the PCM seeing the throttle position (change)?

Yes, the computer is showing throttle position change.