IAT Sensor location

[Allmachtige]

That's great info.....however, that doesn't answer the question:
Where can I see "very well-proven reasons" why the 3.5" ID tubing is better than the 4.0" ID tubing?

I think you might be splitting hairs. If Intense can lay down numbers like it does on 3.5" then 3.5" sounds logical.

The extreme argument would be to just run an open TB, but that's just silly.

[MaxNismo]

on the strip a 3 micron filter over a correctly fit tube going from the tb to where your headlight should be is fine...fwiw

also the bigger tubing isn't helping you...

[PURENVY]

There is only 2 bullitins on the link provided that pertaining to any kind of hp made. Both those cars started out with a 3.5" FWI and then changed to bigger tubing/filter, they also changed from a FWI to an HAI. Both those hp numbers were put down after the switch.

As for the 4" 3.5" debate I really don't think it would make a difference on any Bonneville other then maybe Rogue. I wouldn't bother changing but I do agree that you should get a 3.75" to 4" reducer though.

[willwren]

The purpose of posting on a Forum is to share information and learn from each other. In this particular case, it's clear that some prominent cars producing some serious power are running the 3.5" FWI for some very good reasons.

Laminar flow is the key. Here's a dissertation on the various effects dealing with smaller TB's on the 3800's, but it still DIRECTLY relates to the 3.5" vs 4.0" debate here:

http://www.pontiacbonnevilleclub.com/fo ... 788&p=5379

Basically, any 'step' in size is hurting you, especially if you can't outflow the properly-sized (no-step) 3.5" intake.