Ok, I realize that for experienced tuners this is probably going to sound like a drooling retard question, but I've searched and read some articles about plenum spacers, and I still don't get it. Could someone please explain to me?

 

the stock plenum basically slopes and resticts air to the front two cylinders...a spacer gives more room under the upper plenum to aloow more air to flow to those cylinders...

 

A plenum spacer alters the horsepower and torque curves. Spacers are offered in different thicknesses. All alter the curves differently.

 

Is any tuning necessary after installation, or is it plug and play?

 

no you dont have to tune it...i have a motordyne 5/16 spacer on my car...just install it and go...very easy install takes about 20-30 mins,

 

will 5/16" or 1/2" spacer fit into stock z, or are mods or replacement of any parts neccessary?

 

5/16 from motordyne should keep everythign in tact strut bar and engine cover and all

 

What's the HP and torque gain on average?

 

16 tq 13 hp or something in that area

 

Please check that results of the Sport Z Magazine Plenum vs Plenum Spacer Shoot Out.

 

http://www.mynismo.com/products/Defa...id=2737&v=more