You can run an aftermarket but it has to be recirclated unless you have GM MAS and a MAF-T. Unless you plan on big boost just use the stock valve. It is better than most of the aftermarket ones anyways. I use my stock valve with 22-24 psi and never have a problem. It is crushed though. Stock should easily handle 18-20 with no modification. Remember though that 2g calves are junk, make sure it's a 1g.