I'm not as affected as Ed, as mine was registered in February without any trouble, so I only have the letter from that time frame, but I've obviously followed it closely as it could affect me.
I'm sure Ed can fill you in more as he's really up to speed with it as they wouldn't reg his at all I think.
Of course - I'm running with Tein Springs, Whiteline Droplinks, HKS SSQV Dump Valve and H+S Backbox. The rest of the exhuast wont see March, and it will be accompanied by a remap.
I've kind of given up with the whole warranty thing really.