Any difference in performance from different manufacturers that anyone knows of?

 

Waste of money. There are plenty of other mods out there for the L67 that will add noticeable power, a TB spacer is just not one of them.

Only reason I'd even consider getting one is to have a place to tap for nitrous.

 

I heard it helps to get rid of some knock retard so you can go to a smaller pully. That was the main reason I was looking into one.

 

It does nothing for KR

 

It's still right over the exhaust crossover, so it wouldn't even help with heat...

 

Unfortunately, that's not accurate. It really only does two things. The first is that they are typically made of some sort of plastic to try and help insulate the TB from heat. The downside, as nitehawk mentioned, is that it is still directly over the exhaust crossover. Also, the heat added to the air passing through the throttle body is insignificant in comparison to the heat added by the blower. IMO location of the intake air (stock, true FWI, HAI, "CAI" box, etc) has more impact on pre-supercharger IATs than the couple of degrees a hot TB might add.

The other thing it does is add more post-TB intake volume. One could certainly argue the benefits of adjusting plenum volume on an NA engine, but I'm not sold that it has a notable benefit in an SC setup- especially not on a setup that has the kind of engineering hours into it that a factory setup would have. Realistically, you aren't adding drastically more volume anyways- those spacers are typically less than an inch thick.


My point is, there are no properties of a TB spacer that will add power. It certainly isn't going to drop KR enough that you're going to be able to change pulley sizes because of it alone. If you want a smaller pulley, you need to focus on improving engine airflow (headers, PLOG, rockers, ported TB, etc etc etc). There are lots of proven mods for the L67.