hybridphil

I just switched my presilencer and downpipe to stock cats and left the split air pipe just hanging with no connection. I noticed after driving that my car was leaving round rainbow spots on the ground (gas I'm assuming). Driving at around 30 km/h there would be a spot about every meter...Would this be something coming from my split air pipe? Also I didn't do any soldering of the coupler that I bought so it isn't sealed....could it be that?