Need Help From The MEFI Experts
 

Pr. of 2000 Merc. 502 MPI's (MEFI 3). Rebuilt the stock 415 hp using the 500 hp package recommended by Mark Boos at Precision Marine: .578 lift cam, 2.25 intake valves, 3-angle exhaust valve job, K&N air intake, Gil exhaust, MEFI remapping etc. etc. I also had the stock injectors bench cleaned and tested, 1 was replaced. I'm blown away by the increase in power (9 mph on the top end) and torque. But, here's the gremlins in (I think) the injection system: First both engines show an intermittent miss in the tach. Sometimes after start up 1 or both tachs will bounce a little at idle. A speed run will often make it go away. Other times they're steady at start-up but will show a miss after a run. Next, the port engine has twice only made around 5700 RPM's at WOT instead of the +/-5100 both have been making. After the first time it happened on the way home, it again made 5100 the next time I took it out. Then the last time it again topped at 5700. I put my scan tool on it today and the error code it showed before I started it was #34: Manifold Pressure Sensor Low Voltage, and General Warning #2: Telltale Indicator. I assume that's related to the #34 code, but I haven't had a chance to research it in the Merc manual. After I cleared the code and started up, it didn't set any more errors. Everything was within spec including Manifold Pressure: 14.9 at start-up, 16.9 after warmed up and Manifold Pressure volts: 2.15. I didn't have time to take it for a run. Any ideas or suggestions are appreciated!