P Jay, as I'm sure you can imagine the air rushes in at the front and then piles up at the back end. By adding a tail you shift that high pressure area from where it would naturally sit which is right over No 4.
As far as plenum design goes what you want to do is try to give enough volume and make sure there are no strange resonants, a plenum volume of 10* engine capacity is the optimum but you get 95% of the benefits of the large plenum with just 3* engine capacity. Guess what volume I've been aiming for
The other thing that you want to do is to make sure that you're not getting the wierd resonants where the proximity of the plenum gives the trumpets problems. The ford plenum is incredibly close, just 13mm from the trumpets which is a nightmare, by moving the plenum further away you remove all the nasty resonants. Once you've got an even flow and as close to optimum volume as possible anything goes, going round/square/oval makes sod all difference.
I think we're both making the same point as far as the lambda probe goes, it's reading an aggregate so if the cylinders aren't all filling the same then you're losing power or you're risking detonation or both. Either way it's essential to keep the cylinder filling even.
When I was looking around I kept coming up CNC billets for 1500 or thereabouts, 8-injector setups about 1000 or 750 if it was just a standard plenum with a plate welded on. Of course none of these solved my problem, which was sod all space around the TB, you can see what I mean here:
http://www.g2.nu/chris/westie/pictur...d/img_1908.jpg
http://www.g2.nu/chris/westie/pictur...d/img_1645.jpg
Yep, that's 3mm clearance, the vibratechnics engine mounts are stiff enough thankfully that the whole thing stays put but you can see why I need to move the TB now
Looks-wise I don't give a damn right now, once it's been on the RR and proved that everything is ok then we'll do the pretty one. Right now that's just a prototype to get some numbers, make sure everything fits and works exactly how it's supposed to. Have you got some pictures of the sort of finish that you'd expect?
This is the level of finish that we'll be aiming for:
http://www.g2.nu/chris/westie/pictur...d/img_1869.jpg
http://www.g2.nu/chris/westie/pictur...d/img_1871.jpg