Throttle body, school me

I’ve been around cars since I was ten years old, but for the life of me I can’t figure this one. Why do Toyota use a D shape gasket on the 3.4 throttle body? I took them off and don’t notice anything. Is it Toyota version of restrictive plate?

 

pics of what you mean...

what I want to know is if you can make the throttle on later 3.4s with electronic throttle bodies linear

 

I believe URD makes a circular TB gasket that allows more airflow. I’ve read some threads about this and people overall said they didn’t see any real performance increases or anything.

 

The "flat" creates a bit of turbulence in the intake stream to better mix the combustion byproducts from the PCV system in the intake stream. Note that the flat is just upstream from the PCV port. Without the flat the crud would be more concentrated in the forward intake runners.

The blower kits come with a round gasket because the blower does a good job mixing things up by itself. With the increased volume from the blower there "may" be a benefit from better flow and possibly some thermal insulation from the paper as well.

Since the first blower kits came out, non blower folks would swap in the round paper gasket thinking they would get better air flow and see some benifit. On paper this sounds good but there was no real world benefit. That tiny flat is nothing in terms of restriction compared to the cross sectional area at the MAF/IAT sensors or the throttle plate itself.