Fuel seems like a good place to start. Is it only in third gear (I presume you weren't doing 5500 rpm in 4th, as that would be SPEEDING at 110 mph!)? Will it rev to 6000 rpm in first and second? Fuel starvation usually is most noticeable at full power, at higher rpm. Might be a blocked filter, or plugged filter sock, or weak fuel pump.bosco said:Any other things that might be causing this? Thanks,
If it revs fine in the lower gears, then it is probably not an ignition problem, although a weak coil or a carbon arc in the distributor cap or rotor or even a bad plug can sometimes only show up at the highest load...
Or (gasp!) it might also be engine related. My first thought would be a worn cam lobe. Or a sticking valve (but you should hear that). Or..?
Start with the fuel filter, then the pump and sock (if you are going to install an electric pump, remove the sock, install a metal filter right at the tank outlet, and then put the pump at the back of the car).