you are lean on both banks. you got a vacuum leak, a big ass one at that. you need to replace UIM gaskets, im 100% sure of that. i had the exact same problem, exact same symptoms and all. replaced UIM gaskets and it runs like brand new. its not too difficult to do either, so you should try it yourself

Russell Oval Port 3L Nearly Done MTX75 w/ Homebrew Zetec FD and Torsen Complete