Hey Nige. I'm glad to see you boys are getting your Flappers under control. You also appear to be getting some good help from some knowledgeable people like Luka and Jacques. Going back and forth thru this thread and Twin Cam European Models/German Model, I'm stiil a little confused as to how the SERT deals with your Flappers and whether you need an HDI version. Does the US version work there with the Flappers disabled? With TD's and SE A/C, you won't have any Flappers. [highlight]But is the ECM looking for them, even with the SERT[/highlight]? I don't know, but it sounds like Luka has a handle on it. I see you're already referencing S&S SPO's. You'll definitely be different with them!
I told you I don't speak English. I got as close as I could. Now I see it. Let's go down into town! Not Tunes! Now I know where the New Englanders learned their English! You know I got the "getting loaded with your OL" part though! 
The prices you stated are almost double than prices here. K&N should be $50 and SERT about $460. let me know if you need help getting that here, if the US stuff works for you. Later
Hoist!
8-)
According to Luka the SERT doesn't allow the flappers to operate. This is obviously OK if you change the full exhaust system to one without flappers, but requires some mods if you leave the original headers on and just change the mufflers, but is the ECM still loking for them ? Now that's the $64,000 question. Will it then throw up a fault code ?
I'm not sure if the SERT you use over there is the same as ours' but I don't see why it should be any different.
Thanks for the offer on getting any stuff I need I might just take you up on that offer some time.
Just out of interest how much are you paying for your SERK ? mine's costing