Replaced intake gaskets last year, imrc solenoid and vacuum pots and got the P1507 code ever since. Removed upper intake and retorqued everything, made sure gasket were installed properly, replaced PVC valve and every vacuum line that showed the least bit of wear. Still getting code and idling erratic, code reader is saying problem is "auxillary inputs".
I've also changed the TPS ,IAC, both coolant sensors and all 4 02 sensors
in the last year. I drive a company truck during the week so this truck sits alot the last 2 years.. Any suggsetions ?

 

I'd have to be looking at the IAC even though you have replaced it. Erratic idle and the code seem to point to a problem with the IAC.

Just my $.02.