What is it, what does it do? Any performance benefits in removing/ blocking it off.

 

Sounds like whats usually refered to here as smog. If so it's just a reed valve that allows fresh air into exhuast to help burn any remaining fuel. see stickies above to remove.
marc

 

Hi Graham,

I stuffed a load of hi-temp silicon sealant into the hose marked in the picture to block off the Pair valve! This is the last hose leading to the cylinder head. 10 minute job & let it dry overnight.

There is no performance gain for you but it will eliminate all exhaust popping noises on deceleration. Bill Blue makes block off plates & they work/fit well.....my friend here got a BB331 kit & it was included in the kit.

It is there for emissions & lets small amounts of air into the top of the cylinder head from the airbox to help burn unburnt fuel in the header pipe.

BTW i had to block mine off as the wideband 02 sensor that comes with the PCV & AutoTune is very sensitive & would read the extra air coming from the Pair valve & makes it almost impossible to get a perfect MAP tune, it needs to be just sniffing the combustion gases, NOT the extra clean air getting to the 02 sensor from the Pair valve.
(when people complain about AutoTune not working well it's usually coz they didn't block off the Pair valve).

 

OK got it now. Mine can stay like it is for now. No decel popping, no auto tune. Will see what happens when I go up the extra 30 cc. Hopefully the EJK will flow enough gas.

 

No performance gain, but it sure is nice to get rid of the needless plumbing. Bill Blue's block-off plate is a nice, clean way to do it.