Whuddup!

I have been having a problem since Friday... The check engine light came on... Car is running fine EXCEPT ----> When I hit 4000 RPM it "chokes" and won't rev any higher... It's like it hits a limiter or like the gas shuts off right at 4000 RPM...

I plan to get it looked at today, but I wonder if anyone else has had this problem and if someone can offer some idea of what I'm dealing with.

The only mod is an AEM CAI.... The car runs just fine aside from this rev limit of 4000 and the check engine light. Please help!