Slight idle problems when cold

[Montgomery P-Stroke]

My 03' 7.3 just rolled over 103k miles and is starting to have a very slight idle problem when I get 2 miles down the road to the first stop light. I say slight b/c I've been in a lot of 7.3's that don't idle this good when warmed up. Hooked up the AE today and checked the perdals when the motor was hot...of course #8 was bouncing between 3-4% but the rest were considerably lower. The ICP was at a steady 9% duty cycle but the pressure would sometimes bounce between 450-500 which is what has me concerned. Needless to say it was idling good b/c it was hot when I checked it. What is the acceptable amount of pressure fluctuation for the ICP? Truck has an oem grey cps that is about 8 months old so don't think that is the culprit. Starts fine when cold and idles good (I guess b/c it idles itself up). ICP sensor is original and has no oil in the plug. IPR is still original as well so maybe time for service. Funny thing is that this problem started a few days after I changed my oil to a different brand. Have been running Mobil Delvac 15-40 for the last 50k miles without any idle problems. Just switched to Valvoline Premium Blue 15-40 which is still a dino oil and the problem started. Probably just coincidence but ironic at the same time. Thanks for any help guys.