Like Randy, I also installed the ECI cold induction on my 360 (9.0/1 pistons), AirFlow Performance Fuel Injection, Ram Air.  I had www.aircraftexhaust.net make up a 4 into 1 exhaust from my PVC mockup (turned out quite well).

 

However, my speed gains were much more modest.  I do not have great baseline data, but would estimate my speed gain at maybe 3 knots to ~203kts TAS at 2,500rpm, 3k MSL, WOT.  A somewhat unexpected improvement seems to be noticeably better mixture distribution, which allows me to run lean of peak much of the time.  I have balanced my AFP nozzles, and they generally peak within 0.2 gph of each other.  Being able to run LOP is a great asset for cross country trips.  At around 12-15k MSL, I can generally expect 185kts TAS on around 7gph running LOP.  On a recent trip, I saw 183kts TAS at 17.5k MSL and 6.2gph (KGBD to 39N: 1,126nm, 4.8hrs flight time, 233.2 kts avg GS, 38 gal used, 29.6 nm per gal).

 

My oil temps seemed to increase somewhat, which may not be so surprising given the old sump acted like an oil cooler with the induction tubes running through the hot oil. 

 

(picture attached during mockup of PVC exhaust)

 

 

Also, a cold air installation from a RV builder.  He also noticed speed gains of ~3kts.

 

 

 

Regards,