40's to 45's
I look at it this way:
Going from a 32/36 to a 38 DGAS is a big differance. Especially if the motor is built up. I remember I had to go back to the 32/36 to pass emissions (I had a 38 DGAS on my 2.2) and there was a world of difference in power loss. And I really noticed it when I passed emissions and went back to the 38's. Remember the 32/36 is a single barrel that only opens the second 36 barrel about halfway thru the throttle travel. A 38 is a two barrel design that feeds all 4 cylinders at the same time.
Let's look at some numbers:
On average, a 32/36 is providing 17mm of "air/fuel" flow at a time. And thats assuming both are open.
A 38 DGAS is providing about 19mm of "air/fuel" flow all the time to 4 cylinders.
(38 x 2 barrels / by 4 cylinders.)
This gives us a difference or increase of 2mm per cylinder.
Dual sidedrafts provide 4 barrels to 4 cylinders. This is an amazing 40mm per barrel! An increase of 21mm over a 38 DGAS!
Going to 45's increase this further to 26mm over a 38 DGAS or 5mm over dual 40's.
Were talking a 5mm increase. Remember is was only 2mm that made a huge difference over a 32/36 and 38 DGAS.
So the answer to your question is: It will make a big difference in performance.
(anyone wanna back me up on this. This is probably a crude way to look at from an expert engine builders standpoint. And I'm no engineer either)
And besides. The 45's I bought are brand new. So they look prettier too.
-k