Looking on Ebay, Roadrunner no longer do the manifolds either.....I think there has been a fall out between them and Janspeed
I went to Janspeed to buy my system a few years ago. It was the last 2.8 one they had and the salesman gave me the impression that they cater more for manufactures now like Lotus, where they buy in large quantity orders. And I also got the impression some of the components were made in China now and final assembled in the UK.
I think Motorsport can buy in bulk hence Janspeed will do a run of them. Demand has probably dropped off now, as most people have fitted them and they'll not need changing. Personally I think they became a bit overpriced and had I not got such a good deal at the time I would've probably fitted something else