Fired up my truck after some routine maintenance and i hear what sounds like a knock. I hear tail of stuck open injectors sounding like a knock... Anyone know a good way to tell the difference? Also, theres a way to run an injector test... Do I need a obd scan tool to run it? Apperently the test "Dry Runns" the injectors to see which ones are bad or going bad. Anyone know what scan tool to buy? I appreciate any responses. Thank you!