my truck still runs funny

[19mike69]

my question still has to do with the way it is running....it starts fine,idles fine and runs fine actually...but when you get out on the hiway say,and running like 55 and start putting the pedal to the floor it starts to cut out a little.....it only does it when it gets up high in the rpm's....is that maybe in the timing?...or cap or rotor?...i thought if cap or rotor it might act up all the time,i dunno though....i turned those 2 screws on the front of the carb like somebody told me to do(a half a turn counterclockwise) and i couldnt tell a difference when i drove it again.....what would make one miss and cut out a little at a higher rpm?....btw,this is a plain ole stock 350 that is just going to get me to work and back...i just want it to run right and start right....if you have any ideas please let me know....thanks again