[LX5liter]

When you tightened your rockers did you check to see if you needed any shims under any of the pedestals? It sounds like you may have a valve hanging open. It could be a bad plug as well, just warm it up and spray water on the header tubes to find which cylinder is colder and try switching that plug out. Check to make sure there is spark to the plug as well. If it isn't a plug or wire my money would be on a valve hanging open.