1999-E350-V10-super duty-misfires/no codes /no check engine light

my van is missing very bad-replaced plugs at 75,000 miles-currently 86,000 miles.The shop that replaced the plugs said there is a problem with the fuel injector wiring harness connectors?Is there a recall on this harness or a cheap fix or is it the coil on plugs problem?there are no current codes or check engine light on-is there a test on the coils that I can do?Might have to take it to the local ford dealer for fix-local guys can't seem to fix or want to retire on the fees for replacing all coils and fuel injector harness-can you give me an idea on fees and parts?Taking off doghouse is major job in a work van so need an easy solution-thanks!