06 5.9L Down cylinder?
 

When you take off the oil cap there is an inordinate amount of back pressure. I was told by one mechanic that it must be a broken ring. Also it is idling rough and there is alot of crankcase pressure venting through the tube. Is there anything else that would cause this?
180,000 miles.

Any mods??

None that I know of. I was wondering if the CAT is partially clogged if it could cause this issue? I bought the truck in July

Still in need of advice. If it would definitely be a broken ring where is the best place to purchase a master rebuild kit?

do a compression test and that will tell you if you have a broken ring

i have seen several trucks with scored cyl. and or pistons. we had 3 or 4 trucks this summer in the shop.

like tony said we have seen some also...btw the CR pistons have the top ring closer to the top and i belive that is leading to more broken rings then on the older engines

i test drove a 06 after the guys installed gauges in a 06. the egts were pretty high. no tuner was on the truck. the ecm flash on these stock had some fuel. they run pretty good stock.

yeah then add on top of that a leaking injector and you get some really hot cylinders and without EGT if you may not ever know untill its too late