I've got an 86 K5 with 305 in it. It recently has begun to hesitate badly at higher RPMs. I rebuilt the distributor, so everything is new there. The timing is set 8 BTDC and with the vacuum applied its runs great. The only problem is whenever it sees higher RPMs (not sure when exactly) it misses and hesitates badly. Also, in 3rd (700r4 tranny) going about 45mph into the wind is about the most it can do without missing. Anyone know what might be the problem?