I bet the cold air helped a lot with the faster times, but it also might have been the change is driving technique that was working better for you. Overall your lines seemed pretty good to me. Seeing that GTI struggle to pass you makes me really want to get mine out there, it will probably be a pretty close battle as my GTI is not turbo charged and that turbo one wasn't exactly drastically faster than you.
In the meantime, maybe we should get together to do some racing at the Bandimere Go Karts. They are a blast and wearing the thick racing suits is better suited for the cold weather anyways. I'll have to look, they often have Groupon 2 for 1 deals going there.
Looks like they have a groupon but now go by time, it used to be a 10-lap race. Still a fun deal.
https://www.groupon.com/deals/action-karting-8
I think you hit near 50mph on the front straight in those karts.