Have you tried adjusting the his screw? Or check for boost leaks? Are you on stock coil or cop?

Is your bov recirculated? You might want to check out the tps also.

I am running a stock coil. No boost leaks and no the bov is not recirculated. I have no adjusted the screw. Where is that located?

You should connect it back up, then have the car tuned.

For me it's really hard to start with the coolant temp disconnected. Yeah it would run a little richer but not sure why they liked that idea...

Check to make sure all connectors are cleanly plugged into and around the throttle body

With the coolant temp sensor disconnected you should have a CEL, code P0115. Check for other codes too
Plug it in

If that's all good check out your TPS / idle switch to make sure it's adjusted correctly
(scroll to bottom, 2G adjustment)
RREs  Eclipse 2G Turbo 1G Throttle Body Swap

When ya get all the easy stuff out the way do a BOOST LEAK TEST (BLT)
2G Turbo DSM Boost Leaks -How to test and fix

It's unlikely the BISS screw is the culprit. Don't play with it, unless you have DSMlink to see the ISC position. Just makes sure the screw is actually there and not completely missing

I just fixed my bad idle do you have a 1g TB or 2g if its the fist Gen you might want to check witch tps it is you need the 2nd Gen on a 6 bolt swap I would also check the iac if its bad. Also like they said you need to recirculate the Bov.

Yeah, i knew it was that screw.

Did the op ever figure this problem out I am having same issue only it is t 2500 rpm it's 1400-2000 rpm

Well, what have you checked so far

Having the,same issue on my 2 g 6 bolt swap , it threw a tps,code