engine missing out bad could it be cheap cap?

[jd-underdog]

my car is running like crap. when the rpms get up to around 3 grand or above in 3rd or 4th gear it missies out bad. when i did my tune up all the parts store had was a carappy cap with aluminum contacts, could that be my problem? what is a good cap, just any cap with the brass inserts? thanks for the help

 

[bmorrisj]

check spark plug gap too...

 

[jd-underdog]

i have put 2 sets of plugs in gap is good motorcraft plugs, also has good ford racing 9mm wires wich are only 2 years old