testing for a bad poppet valve

I was wondering how to test the fuel injector poppet valves, the TSB says "use strategy based dianostics listed in front of drivability and emissions section of service manual." I believe they r referring to the OEM service manual. Anyone got any idea's? I can't count on the dealer to check it right, they already 3 tries at my expense.

The dealer should do an injector balance test to determine if there is a bad poppet/injector, the test is usually done the same time as the high pressure injector cleaning.

If you have a handheld scanner that tells you what cylinder is getting the misfire you can switch that injector into another cylinder and see if the misfire follows it or not. You can get a scanner for like $100 I believe.