After driving in traffic on a hot day it runs rough and PO302 code comes up. on 1996 Ford Ranger

Runs fine, let it sit for 20min then start & it runs rough & PO302 pops up. Turn it off let cool down for awhile & then its fine. Replaced coil, plugs & wires and fuel filter. No overheating, temp gauge is good. Could it a intake manifold gasket leak or bad fuel injector? Only happens after driving in traffic on hot day, runs fine, shut it off for 20min then start up & rough idle & PO302 code.

by in Burbank, CA on August 25, 2013
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2 answers 2 comments
ANSWER by , August 25, 2013
Try some injector cleaner with Chevron Techron. If that dont help after driving awhile, a week or so, have the injectors professionally cleaned. Possible vacuum leak but not as likely as an injector problem. Since you have installed premium ignition parts, i'm sure (?)
COMMENT by , August 31, 2013
I belive that solved the trick. I added a bottle of Zmax to the oil (suppose to clean the internals of the motor) , then added a bottle of Lucas fuel injector to the tank and filled up with 91 octane at Shell, once i got down to half a tank i refilled with 91 octane and added another bottle of injector cleaner. Then drove up to the Sequouas (235 miles) at 70-75 mph. Ran great had no problems plus i got around 24-25 mpg, never got that good ever.
COMMENT by , August 31, 2013
COOL!! Thanks for letting us know!
ANSWER by , August 26, 2013