I want to put on cams and arp head studs and k16 in while I take the the head off to replace my head gaskets in my 07 s40t5.
What brands should I be Staying away from?
what would be a good tuner to buy. Will it be Able to pass smog with these performance mods ?

 

regarding smog testing for your car - Don't think the head studs will make a difference :-) will a bigger turbo impact emmissions? my guess is probably not - the turbo is just an air pump - its the ECU tune that has the job of managing the air/fuel mix. Most states do their emissions using steady state readings, ie NOs and HCs - in CT I recall the tests running on a dyno at 2000 RPM. Assuming you don't have a check engine light on, your cat is still on the car and its in good tune, you should pass. In terms of tunes, there are two types = those that overwrite the fuel mapping but use all the original sensor signals and those that alter the sensor signals to create more boost. For your interests, if you are going to a stage 2 with a bigger turbo, I'd go with a tuner that has a package that matches your design. Elevate, ARD, Rica etc all have packages. You can also consider a product that offers selectable programs - ie stock for running 89 octane, stage 1 or 2 for running 93+.