Ok, I am boggled about this setup. I was told that when I setup my 240 for a turbo to run 2.5" hot pipe to the intercooler and 3"?, I believe, to the throttle body.

Why would one step the size of the pipe up AFTER the intercooler when the air is more dense and can be packed into a smaller area?

Is it simply because of the transition from a 2.5" cold pipe to the 3" throttle body would create a restriction on the flowing air or what. I would think you would lose some of boost, or create non-needed lag, when stepping from a 2.5" hotpipe to a 3" coldpipe. With the air being much more dense after the intercooler stepping to a 3 inch coldpipe is similar to just running the hot pipe into a 3.5" or bigger coldpipe (w/o the added benefits of colder air).

Sooo...Why would one go a larger pipe size on the cold side of the intercooler, in theory you could probably DROP a size and create no loss of flow or boost pressure? Right? Wrong?