If you do not have an open port between the head and the throttle body the best thing to do it tap one. Assuming your not using AN hoses go to a hardware store and buy a 1/8 npt to barb conenctor, a 1/8 npt, tap, and whatever drill bit it wants. Drill close to the throttle body if you can and shove a rag back there to catch filings. Grease on the bit when you drill helps also. Don't splice lines to get a reading. You want a dedicated one on the manifold after the TB