Its injector connectors 2 and 7 that have the most issues. More details will help, does it run bad? Check engine light come on? any codes? Have you inspected all the usual wire chaff areas? (Google it) Have your balance rates checked with a scan tool.... 300K on stock sticks that are original sure adds an injector or 2 to the mix. So more info is best and cheapest for you, Because we can give you a short list of expensive educated guesses and common parts to replace that will make xmas a little short on cash this year. Good luck.