91 M5 problem during full acceleration, help appreciated

[icm5er]

Well this year I finally decided to enjoy my 91 M5 with 52k miles. For the past 3 years of ownership, it has been a garage queen, pampered. Lately, I have been driving it often, putting anywhere from 100-150 miles each time I take it to work. It has been running flawlessly, as would be expected from a car with only 52k miles and extremely clean.

Today however, I noticed that under full throttle, in third gear, at around 5500rpm it lost power, like when you drive a car that is very low on gas and it is ready to quit. At first I thought it may be wheel slip due to uneven pavement under hard acceleration.

Over the next 10 miles or so, I tried a few more times to duplicate the problem and sure enough, only under full throttle, accelerator fully depressed, at 5500rpm it would loose power, in second, third or fourth gear, it seemed to be getting more pronounced. Other than at 5500 rpm though, the car pulls strong like usual, throughout the rest of the rev range.

Three hours later on my way home, I tested it again and only under full throttle, it lost power but it seemed even more pronounced. Over the next twenty miles or so I tried gradual acceleration and the car runs fine, from stand-still to 6500.

So my problem appears to occur only under full throttle at 5500rpm, other than that, the car runs strong and seems fine.

What could be the problem?? The car needs nothing, all maintenance is current, fuel tank is full, gas is 93 octane.

Thanks in advance.