In order to idle around 800-900 I need to close the BISS completely. The ISC sits at 54 steps once warmed up. If I engage the BISS adjustment the car nearly dies, so the ISC is obviously capable of going below 54 steps. I have also tried 2 different ISCs. Any guidance is appreciated.

 

It looks like it just needed some driving to get the ECU to make adjustments. The idle dropped way down today and I was able to get things very close. It's only 100 to 200 RPM high when properly adjusted, so I think it just needs time to finish learning.

 

In before Right Said Fred says it's your fuel pressure.

Sounds like you could have a vacuum leak. no amount of closing the BISS will compensate for that. Have you checked, by chance?

 

No vacuum leaks, I put in all new high quality silicone ones. I also sprayed around looking for leaks. One possibility is I may have hooked something up wrong when putting on the lines after changing the intake manifold. I will try to find a good diagram to double check with. I also checked my vacuum and it is right around 21 inches.

 

I had the EGR valve control, the red round one, hooked up backwards. FPR goes straight to the manifold right? The idle is now able to go below 1000 RPM!

 

Ah. That's a check valve. Very important to get that right. Congrats!