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Message: [QUOTE="Holeshot, post: 1565350, member: 33721"] I was wondering if anyone could help me out with a diagnosis. I've got an 07 6.0 that I bought off of a friend relatively cheap, as it was going to need injectors soon and he just didn't want to deal with the truck anymore. Let me preface with saying that this truck had a lifter failure, and he put in a DDPM Stage 1 cam with 100 lb. valve springs, XDP chromoly pushrods, and ARP 425 studs with Fel-Pro head gaskets. However, he did not machine the heads and only checked them with a straight edge. The truck has a coolant pressure gauge on it off of the shorter degas bottle line at the front of the bottle. Since he had owned it, coolant pressure would be around 7-9 psi when up to operating temp. You could vent the cap at operating temp, and the pressure would rise to about 3 psi after that. It never consumed any coolant or puked any out in this timeframe, and actually drove across the country from San Diego to Connecticut with no issues. Since buying the truck, I replaced the injectors with Holder's Premium 190/30s, an XDP regulated return, and an s363 (I can't leave anything alone). I am running Gearhead's reduced fuel tune and when laying into the throttle for prolonged periods of time, I will see the coolant pressure jump by 6-7 psi. Even after venting the cap at operating temp, and continuing to lay into the throttle, the coolant pressure will jump from 0 psi (after venting) to 6-7 psi, and then add around 6-7 psi with every pull. The truck hasn't puked any coolant, nor has it consumed any coolant. If it is driven without flooring it, the coolant pressure will stay within that 7-9 psi range that I had mentioned in the paragraph above. I have a tow tune from GH as well, and the coolant pressure will sit at 6-8 psi, even with me going WOT. The coolant pressure rise seems to be from anything more than 35 psi of boost and I feel like I may have a head gasket issue on my hands from improperly prepped (or in this case, no prep lol) heads. Or is this more of a momentary lifting of the heads with these WOT pulls, and otherwise they are fine? Any input would be greatly appreciated. [/QUOTE]