Truck just started to not idle at startup when cold. Have to keep a brick on throttle to let it warm up and then it will idle... at 500 rpm. Will start fine later in the day and idle fine but then it starts doing it again. Had a code for misfire from 02 sensor but now it cleared itself. Checked for stored codes last night and nothing. Has new battery since old one was shot. Replaced heads and all the other goodies a year ago at 103k and ran like a top until now. lost oil pressure as I’m just typing this. Seems to drop when I let off throttle and then the idle drops more