21/07/17: Lordy! Honda conversions!! These take up more of my time than dronnnnnning exhaust questions. I had a very expensive Honda 4-2-1 manifold stolen by an Exige owner in Yorkshire, so I have changed the way I deal with the sale of this particular manifold. Nothing leaves my workshop unless full payment is received beforehand.

21/05/2018: A lot of Honda conversion don't fit a proper catalyser. Here's a recent modification I had to make to ensure the car passed some strict European emissions tests. Most conversion catalysers concentrate on POWER - so they use 100cell Racecats. Useless for passing any emissions tests. Been there, tried that.

So, you go from this - 

 To this! - 

 I use the very high-quality German HJS catalysers. Used on all the World's supercars, they have a good weighting of the precious metals needed to actually CATALYSE. I use the 130mm HD version for the 4-cylinder supercharged installs and all the V6 motors and the smaller 121mm version for all N/A installs (shown above - no room on an S1 Elise for the bigger diameter!