97 Sunfire Power Reduction @ 4000 rpm

While driving my 97 Sunfire 4 cyl with automatic, the other day it began to display an odd behavior. The engine seems to display "redlining" behaviors at 4000 rpm, and will also reduce power to the engine. At idle it idles smooth, and rev's fine all the way up to 3500 the its seems to slingshot to 4000 then back to 3500 rpm and will continue this cycle as long as you keep it steady or try to rev it higher. I drove it around town today, and while rolling down the road, I put it into neutral and rev' d it up, sometimes it would display the

4000 redline behavior, and other times it would let me rev all the way up to 6000 rpm, but more often than not it has been displaying this problem. ANY IDEAS??? Thanks