What upgrade options are available for the standard E6 turbo in terms of increased flow....over 400bhp? I know that you can get a roller bearing conversion keeping the same size internals through essexturbos(?) but is there anyone doing compressor wheel changes etc.? I believe that the fact that they are reverse spinning means that the common compressor wheel swaps are not available. If converting to an opposite (normal direction) spinning turbo I assume that you need a new exhaust manifold, and am I correct in assuming that there would be a trade off in increased lag over the reverse spinning variant?