I recently changed my plugs and now the car rides rough and I got back underneath the car and saw this little rectangle shaped thing that has a red led on it and it is halfway burnt up from sitting on the passenger side collector. Does anybody know what this is and what it does?

 

Pics would help a ton, but just guessing it's probably an aftermarket alarm or other wire for radio etc... Nothing installed by GM in that area has a red light on it.