i recently got a new 4runner, after recking my other one and i put some performance exaust on and the check engine light comes on every so often. And i have heard that they can come on because of emissions reasons could this be the reason or could this be something serious.

 

There really is no way for us to tell. Go get your code read at a shop to find out if it is a serious problem or not. Better safe than sorry...

 

or....
Just use the jumpers and figure out what code it's throwing cause then we can help you much better. There should be something on here that shows how to jump the diagnostic box. Try a search on this site. Good luck and let us know how it goes or what code you get.