My 2005 6.0 has had a lost in power recently, normal driving everything seems fine, but at WOT the truck will shift through the gears, then hold at 3000 rpm in 4th gear then doesnt shift again until i let off the gas, boost pressure has also dropped too, i topped off the coolant about 3 months ago and had to add about a gallon to it yesterday, it does the same thing stock and in a performance tune. It did this once earlier in the winter but the problem didnt happen again until recently. I need to replace the air filter, because thats way over due but that cant be causing the problem can it? it has 201,000 miles, still has factory egr and head gaskets. I cleaned up the egr valve to see if it would help with the problem but got no response from it. Also on an average temperature of lets say, 0-15 degrees, the turbo does not give any boost, like the vanes are shut, until the truck gets to operating temperature. Is this normal for the turbo? i work at a dealership and had to get an 06 6.0 started after being on the lot for a month and the turbo spooled right up, it wasnt plugged in ever and it was 2 degrees out.