I just finished up a 700R4 to T5 swap. I have since put on about 350 Kilometers (217 miles). The last 100 of that I've been dealing with an engine at 2000 rpm between shifts. It's been getting progressively worse. When it began it was the odd shift. Now it's every shift. The car isn't even decelerating very much, at least not below 2000 rpm when in gear and slowing down. Once I push in the clutch, it goes right up to 2000. As soon as I kick the the throttle it comes down to below 1000. It only does this when I'm driving. If I'm sitting still and in neutral I can rev the engine with no issues. As soon as I start to drive and shift, it's at 2000 until I kick the throttle. I have heard that the automatic PROM could cause idle issues, if that's what this is then that's fine as I'm waiting for a custom PROM for a 5 speed to arrive in the mail. Other than that, any ideas?

 

I ran my car with an automatic PROM for maybe a hundred miles or so and never had an issue. Doesn't mean that isn't your specific problem. Only time I had one stick like that it was a problem at the throttle shaft, it would hang up and not close all the way when you laid off the throttle slow enough.(they also tend to give a small vacuum leak since the bushings are worn) I added a return spring and the problem went away which made me know I needed a repaired TB.