help with my new white Bros Pro aluminum exhaust.

[clancooler]

I just got a white bros Pro Aluminum Full Exhaust and Header for my dvx400. it runs fine with airbox lid on and stock jet (130) but I want to run it with the airbox lid off. i have a 160 jet that came with it, i have installed it and ran it with the pipe but it back fires when i give it gas. The instructions said to run the 160 jet when the lid was off. It also says to tune the air screw if theres too much gas or air in the mixture. I just thought id get a little advice before i go screw with things. i have not had time to see if the stock jet would work with the lid off, but i think it would run lean.

[ZRIDER]

You need to run a bigger main jet.  I have a 185 in my Z with a full FMF and K&N with no lid. 

[clancooler]

well i need to get a jet kit in that case, ill just run it with lid on till i get one then.