I have a 99 F150 Supercab 4x4 with 187,000 miles on it. It has the 4.6L Triton engine in it. No problems with the truck until recently I have been having an issue with the truck running rough at an idle and the Check Engine Light coming on and off. The light will never stay on for a long time. So I took it to a Ford dealer near me. They said that I have low compression in cylinder 6. Upon further discovery of digging deeper into the engine, they said there is an exhaust valve leak. They are not for sure if there is a burnt valve or if the head is bad until they get deeper into the engine. Both of these repairs are big money and questioning if this is really the case. I had another opinion from another mechanic from an independent shop and he said that maybe there is just a bunch of carbon buildup on the valve's. That mechanic said that they can hook up a machine that put's a chemical into the engine to clean the carbon off of the valve's. Costs around 110.00 to do this. Anyone have suggestions on my next steps? I am by no means a mechanic, so looking for options at this point. I have considered trading it before I found out about this issue, so if this issue is legit, I doubt I would get that much money for it for a trade in. Thanks in advance for any help!