Montero idles rough

Posted this on the Montero forum and got some good input, just trying to get some more opinions. Battery hooked up backwards-(Don't ask!)- Changed radio fuse and Alt 100 amp main fuse that were blown. Car now idles fine cold, gets real rough after warm. If I baby throttle past idle, it will rev fine. ECM not giving any codes, even with sensors disconnected. IAC, throttle position and coolant temp sensor ohm out fine. Dealer says new ecm needed, and along with that, immobilizer ECM and ignition key reformat. Need more opinions before I fork out almost two grand! It's a 2000, 3.0 liter, LS. Got two different suggestions for fuel pump control module.

Double posting will not get you an answer any faster

I'll stay in Montero forum, thanks