302, holley 4777c carb tuned to run 13.5-14.5 AFR anywhere between 2000-3500 rpm (wideband o2 says). ign. advance set for best vacuum 1:2.7 gears, 235/55/r17 tires. when driving for a longer trip (50+ miles) it starts to have sloppy acceleration. does not overheat. even old carbureted vw with 1/5 of 302 displacement accelerates faster. what would you suspect?