The manifold I have for the motor was made by cutting down the original inlet manifold head flange and welding on some new runners and flanges to suit the 45mm toyota throttles. This is a perfectly fine proposition and works well, however given the nature of the motor we are searching for every few horsepower we can find, so the decision was made to correct the flaws in the design.

I must make it clear, the "flaws" are really sacrifices made to fit the throttles into an E30, this is because both the thermostat housing and the brake booster causes clearence problems, so the runners had to be bent or offset to clear both items.

Fortunately, there is an alternative with Rowland Manifolds offering an "off the shelf" manifold to fit the M20. As with all manifolds for the M20 the brake booster is still an issue.

However because the RHD E21 utilises a booster on the right hand side of the engine bay suspended on a long bracket and linkage, there is nothing in the way preventing their use.

While RHD owners usually curse bmw for placement of components (especially manifolds), in this case, the weird brake setup on the cars actually works to our advantage.

The manifold retains the original crankcase breather, a huge relief personally as it saves a load of hassles trying to design something to reroute crankcase gases back into the motor somehow.