I used to have that "after 4hrs" thing (or basically in the morning and after work). I fixed it with replacing all the vacuum lines (which you did). I also replaced the crankcase vent / oil separator at the same time. Basically it boiled down to misfire.i thought that, but it idle's fine after it does it's thing. after that for the rest of the day it starts fine, runs strong. it only does it if it sits more than 4hrs.