89 5.0 vert car idles up and down slowly its not a fast surging it idles down to 8-900 ish then slowly climbs up to 1700 or so then back down car has new iac valve new tps no vacuum leaks i cant figuer it out any thoughts? Also when its cold you can hold the throttle steady any rpm say for instance you hold it at 2500 and all of a sudden the car bogs and wants to die but only when its cold and when you hold the throttle off idlw steady. Help?