Have a 1999 3.0 flex with lean codes on both banks read from Ron to pull IAC plug while engine is running and warm and rpms should drop if no leak...my truck usually ideals between 800 to 850 and when I pulled the connector it only dropped roughly to 750 to 770 but no further then while iac still unplugged pulled hose from passenger valve cover to air inlet tube(sorry don't know the actual name of it)and covered with finger and rpms dropped to 550 to 600(running real rough) hooked the hose back but left iac unplugged and the first line I pulled off the manifold the trucked died immediately so can someone please make sense of this....also back story just had exhaust fixed from pipe rusting and broke so new exhaust from behind cat to tailgate but had rich codes before that but now lean codes???have ordered new maf sensor...please help...reach out for more info