Wow...I can't believe I just read all 7 pages of this thread.
Here's my imput and testing results. I do not have dyno sheets to prove the power just decreases in ET...which was and still is more important to me.
When I was on my quest for STOCK MOTOR NA 12's I tried a few different set-ups. I started with a custom Ram Air set-up that I made using a
K&N 12" cone filter, the car responded with a crisper throttle and slightly more mph at the track. This was over a stock set-up minus the siliencer, and a K&N filter. So the addition of the ram air did do something...
I then upgraded to a 75mm Bullet Pro-M sall very minimal if any gains over the stock set-up...still a stock motor.
I was able to get into the 12's (12.89) with the stock air meter, but was never able to go faster with the 75mm on the combo.
I built a new combo shooting for NA 11's, started off with the above ram air setup using a 24# inj and the same 75mm Bullet. It ran well but I wanted to try different things, I upgraded to a 76mm C&L and air tube and the same ram air set-up and it ran good but I had some a/f ratios issues as it was lean up top. I was rewarded with a few more mph (2) and a quicker ET. I tried to make my own power pipe however the C&L needed to stay in the stock location, it could not read in the inner fender. I noticed the car would run better with the K&N air filter off the car, so I put the stock air box back on my car, mated to my custom ram air set-up and the car was faster in all the 330, 1/8, 1/4 etc. I was shocked to say the least... I then swapped in a K&N panel filter and to my surprise the car slowed down, swapped back to a cheap paper filter and it went right back.
I then tried different TB, swapped the 65mm out for a 75mm and went 2mph faster and a few tenths on back to back testing at the track, similar 60ft's, air temp, car temp, etc... so the larger 75mm TB on my 8.8:1 NA 302 was worth some power (I shifted at 6600rpm), datalogged it all on my Speedbrain as well. I also upgraded to a 30# inj since I was pretty lean with the 24# according to all the dataogging I was doing.
I ran the 76mm C&L air tube, 76mm C&L meter,m 30# inj and the stock airbox, and the 75mmTB and was running 12.0's at 112-112.8mph. I swapped to a 80mm Pro-M and was rewarded with my first 11.98 @ 113mph, eventually got a best off 11.96 @ 113.6mph.
The car was a little smoother with the Pro-M and I was happy as the drivabilty seemed better over the C&L so the 80mm Pro-M was worth the upgrade. I then decided I wanted a AFM power pipe, and I was getting the HV version 4" pipe. I put that on the car and with no other changes the car went 11.80 @ 116.7mph, and the car made more power across the entire rpm band based on my dyno calculater in my Speedbrain. (I found it was only off 2hp from my Dynojet readings). The car was smoother, pulled harder and seemed to run better in the heat then in the past. I was using on of the AFM open ended filters and still had the inlet of my custom ram air hooked up at the fog light hole.
I took the car apart at the point to build my new adventure, NMRA Drag Radial car.
Was the AFM pipe worth 20hp on my set-up...no but it did increase power and showed that I did have some restrictions with the other set-up's, that were straighter. I feel most of it was due to the larger ID piping and my motor was able to take advantage of the air.
We have done some other testing and have seen a straighter airpath with a longer tube make a few more HP on the dyno, still larger I.D tubing though, alum.