You're right, I've owned modified cars for a while and I've never had an issue.
No fine, he said he wasn't going to fine me, only warn me. Probably because I was being honest and cooperative. Kept asking me if it was my car, that was annoying.
I just think swapping the exhaust over mightn't be the best idea as I drive the car every day and I'm bound to get done again. I'll speak to the exhaust shop about adding a hotdog and see if that would get it legal?