I'm currently having a few problems with my Ute which is that its running really rough at higher rpm. The engine feels really strong at lower rpm and starts to pull but when the revs reach about 6000rpm the engine has some sort of miss and struggles to rev any higher. It seems to be really bad in 3rd and 4th gear, it still has a miss in 1st and 2nd occasionally but not as bad. I first thought it was electrical as I have replace the coil, points, condenser, HT leads, and spark plugs but it still remains so now I'm thinking its the carbs (twin dellortos) and is a fuel related problem, I've checked the float levels fuel pump, fuel pressure (set about 2.5psi).Do carbs need re-jetting over time to suit the motor as its done about 9000ks since rebuild. I was also wondering if a vacuum leak would cause this?

Any help we be appreciated.