high idle problem

Update...I ordered a refurbished throttle body on eBay. Unfortunately it was for an auto transmission. I did a bunch of retooling and hooked it up. It purred at 9000 RPM. Then when the engine warmed up it jumped back up to 1500-1700! I did a crude smoke test and found no leaks.
I can't remember if I replaced the manifold gaskets when I did the valve cover gaskets. Could this be the problem?
Or a bad ECU? Thing is it just happened after the valve cover gasket job. So why would the idle jump after it warmed up with the new TB?
So fustrated. Looks like I might be taking the plenums off to check if I replaced those gaskets.
I was going to send the original TB to Maxbore but sounds like he has passed away.

 

Remind me have you checked the TPS yet? Either function test it with a multi-meter or check the throttle position sensor signal at idle via OBDII.

Got pictures of how you "retooled" the throttle body? Kinda sus of that working as intended

 

So it idled great when I tested it with the new TB. I had no cables connected. Now, high idle, even with cables disconnected.

 

Did you retrofit a dash pot on? Can't see half the throttle body in that photo

 

Yes. Put a new dash pot on the original TB. The photo is of the TB for an automatic. No way to put a dash pot on the Auto TB.

 

Yes tried 2 different TPSs. I'm thinking I might have messed up a grommet in the valve covers or something similar. I'm going to take it apart completely when. I get some time.