I have a 1998 Four Winns 25 foot Vista Cruiser. It has the Volvo Penta 5.7 GSI motor (57FCPBY). Up until this year it has been a very dependable motor. When you start the motor, the engine idles just fine. When you take it up to 1,100 or 1,200 rpm, the motor starts starving for gas. The...