I have a 1990 Plus 8 3.5 EFI which I've had from new and has 32K miles on the clock. It has developed an engine noise at exactly 2600 rpm, take the speed up to 2700 and the noise disappears. It is a very high pitched whistle and my initial diagnosis was that it sounded like air being drawn into the plenum chamber or maybe a hose connected to the plenum chamber. The noise is exactly the same irrespective of engine load. Due to general engine noise it is difficult to determine which area it is coming from. I am going to remove the fan belt to eliminate the alternator and water pump but I believe this is a long shot as it is not your typical bearing noise. I'd appreciate any suggestions, particularly if you have experienced this type of noise on you +8 EFI
