[C. Ludwig]

Pressure in the manifold will be a cumulative of manifold and tail pipe pressure. It will always be higher than tailpipe pressure. If you're mapping your fuel map as a MAP v. EMAP, you'll need to know manifold pressure. Tail pipe pressure is useless for this calculation because it disregards manifold pressure. Monitoring tail pipe pressure is only useful in a sense that you want it to be as low as possible and therefore would want to know if it's relatively high.