I had something similar occur once with my 89 Plus 4. Running at 3500 to 4000 rpm it would suddenly cut out. Once the restarted it would be fine until the next period of similar revs.The answer ( hats off to Go Mog ) was to replace the alternator. The problem never reoccured. After I had sold my first 4/4 the new owner had the same problem and once again an alternator change solved it. Coincidence perhaps.
