121k on the vehicle. Seemed to be running fine until last week when it started misfiring on 7&8. Replaced all spark plugs and the coils on 7&8 and it was a little better but not great. Took to mechanic and he mentioned possible valve issues but wanted to try to clean the valves first. Ran mostly fine Monday and almost all day Tuesday but then lost pretty much all the power and started missing really bad. Going to get a compression test done today but most likely will have to get the valves done. Mechanic said 2600 for it but says it will fix it and should run for a long time. Anyone have any experience with this? Thoughts on price? I can't sell the truck as is. Don't mind spending money if it fixes it and I can get another 75k out of it.