Installed Cosworth replacement air-filter in my A-Star. Apparently Cosworth are the only people with a replacement filter available for the A-Star last time i checked (which was a month ago). Filter medium is Cosworth's proprietary non woven synthetic material and the best part imho is that it is an oil-free type, so no oiled MAF sensor if you happen to over oil the filter. The recommended cleaning procedure (after 10k Kms as per them) is to soak the filter in mild soap solution and washing it under flowing water inside out, and drying naturally.
I did not expect any huge improvements in performance after installing this, but i'm pleasantly surprised about the fact that the car feels a little more peppy now, even with AC on, and it builds revs more quickly. A-Star has a typical jerk (reported by many) when throttle is let off, in slow speed city runs this can get a bit uncomfy, now after the filter this symptom has reduced by a fair amount, car feels much smoother.
The stock filter was not very dirty to begin with as you can see in the pic, so the improvements i noticed with Cosworth must be genuine.
Edit: As you can see in the 4th photo, the K10B airbox looks a bit small.. i was wondering if the K12B airbox from Swift would do any good here. From the pics i've seen it looks like the K12B airbox can be squeezed in there. Any thoughts?