Got this fitted on saturday; basically its a big shiney alloy intake pipe that replaces the second resonator chamber and all the plastic trunking around to the AFM. It forms a much larger resonator chamber than stock.

Took it for a good road test on sunday (club run into Armagh), Well, when the car is cold, throttle response is a bit spluttery, but only for 30s or so. After that, the car seems to rev much more freely than before. My car seemed to have a bit of a flat spot around 2500 rpm (not due to the plug leads). Thats gone. ON the flat, motorway, at 70 in fifth, the engine used to turn over at an even 4000 rpm. Now its 3800 rpm, on the same bit of road. Hmm...

I got this cheap, used. Probably not worth buying new (I think its nigh on £200 plus shipping from Japan), but if you're handy with metal fabrication, might be worth knocking up you own version. Piccie of the 1.8 version here, down at the bottom. 1.6 version differs in that the resonator chamber hangs vertically. http://www.speedlab.com/miata/mmexh.html (1/01)