The unported BBK sucks compared to the unported LSXRT. The Mamo ported LSXR follows better than the unported LSXRT. Opinion based on data vvvv The BBK without lots of porting, lots of testing and lots of expense isn’t going to out flow a Mamo ported Fast LSXR intake manifold in a cathedral application regardless of which cathedral head stock, ported or aftermarket is sitting under the BBK manifold. The BBK is a terrible starting point for an intake for an air hungry 427 that turns ~6,200 rpm