TRI-Z air filter

[Sinbad46]

Hi, i have a TRI-Z 1986 with UNI foam air filter, what's the difference with a K & N air filter?

And i have the original exaust pipe with DG silencer....if i want to put a DG exaust pipe, which type of modif do i make to my bike....(Carb jet, air filter, etc...)

thanks