Have a 97 Monte Carlo 770, for the last couple of years runs doggy at mid and high rpm's. Act's like it floods out or runs out of gas. Put a new fuel filter in the other day and noticed that the filter is completely empty when running, soon as I turn off the engine it fills back up. Don't think this normal at least my Yamaha has fuel in the filter while it's running. Went through the carbs 2 years ago and it still had trouble, only used it a couple of times since. Was using it in some rough water a couple of years ago and wonder if something may have come loose in the tank or somewhere. Blocked the return hose for a few minutes while running it in the driveway, then revved it up and it seemed to run okay with out bogging down which it usually did after about 15 seconds at high rpm. Any ideas ?