Thanks everyone for your responses,Turns out everyone somewhat hit it on the head, because we had good compression it was a hard problem to diagnose,Actually it was a cascading # of issues that led to the severe skip, once we pulled the head off, we found a cracked valve on #2 cylinder, also the cam shaft had excessive wear, all replaced and assembled, once running we had a slight skip and ignition in exhaust,turned out to be fuel injectors, than we had a RPM surge at idle, which was worn gears in throttle body, Then hard starting and excessive lp fumes, Yep fuel regulator, I thank its save to save it was a expensive project close to $4000, list price, would have been cheaper to throw the truck away, and replace it. worst part is the fuel components were replaced in the past. Iam not sure fixing these animals is worth it like the old trucks we grew up with.

pull it apart mate, your valve seats will need repaired

If this a v6 engine has the sparkplugs been changed recently because they are awkward to change???

With 12000 hours... Could be a few things.... bad injector , or the fuel filters are clogged. Dont try to clean the injectors just replace them. Check the fuel rail also.