The 4750 is an oval filter. the hole is on one of the ovals half way between the outter edge of the filter and the hole for the pipe.

This is where you want it if you put it in the pipe.




See the shiny black cap? This is where you want it in the filter (preferred). I moved mine back and forth for awhile for testing, but my harness on both of my cars was long enough already.

The TB reducer will be a 4" to a 3". Go to a turbo shop or online turbo shop and they will have them. Typically Pep Boys only carrries from max 3.5" to 3". But it'* better to spend a little bit more and get better quality stuff than to regret it later and have to buy another crappy piece. Just my two cents.