300sdl won't rev past 3k under load

[chuckfryer]

Hello-
I have a 1987 300sdl. It's acting very strange, it revs freely in park with no load. It takes off from a stop fairly well, the 1-2 shift occurs over 4000. After that it won't go past 3K. Boost is at 14 PSI until it hits 3000 then falls off. I have replaced fuel filters, swapped out alda, even took the Alda off for a test drive no change. This may be pure coincidence but I will tell you anyway.it started happening after I put a new thermostat in and replaced the three prong coolant sensor at the upper radiator hose. Please help me get this car back to being drivable.

Thanks