I changed my plugs wires and cap. about 2000 miles later started misfiring on one cylinder.. found the wire inside the cable about an inch from the plug just disintegrated??? replaced with better quality cables and it happened again on the same one in the same spot.. about an inch of wire just missing? ANY ideas?? swapped plug again also.

I just recently started having an issue starting the truck after it sits for a day or so. Just all of a sudden.. the longer it sits the longer it takes to start. Getting good spark at all plugs at the moment. Cleaned MAF and intake and replaced fuel filter... any thoughts? thanks in advance guys.