Decelerates Over 60mph

[whodean]

I have an 89 s13 240SX manual drive that is experiencing the following problem. The car runs fine until it reaches operating temperature. Then if you accelerate above 60mph, or about 4000rpm, the car decelerates...it is very similar to taking your foot off the gas...it then "recovers" at 3000rpm. This behavior is repeated anytime you go above 60mph.

Have had two mechanics look at this...did many of the standard things like check and clean the injectors, new plugs and wires, new distributer cap, etc.

They are stumped.

[frapjap]

Welcome to NICO! You might want to search for some vacuum leaks or have the MAF tested.

Do this test and see what comes of it.

How to find a vacuum leak
- check for vacuum leaks. Do this by getting the car running and spraying carb cleaner around any and all vacuum hoses (one by one) and listen for the engine to rev up. If it does, spray again and isolate the area and potential hose. Replace it and see if a difference is made.