Normally when people stack they go the 65/178 route which makes around 1-3 psi more than the 185 or 62 setup.. so stacked runs anywhere between 20-24 pending on Sea level. And honestly I've never heard of any type of boost regulater for our car, I could be wrong though on that . Biggest thing with stacked will be battling fuel and cooling mods. You would need a Heat Exchanger, isolation kit and probably cooler plugs at the minimum for the cooling. I'd throw in the killer chiller as well.( I have it and it works wonders. For fuel you'd need a 55 fuel pump, updated IC pump, bigger injectors. And honestly probably a fuel regulator. Probably all in all about $2500-3500 in support pending on the extent you go. Plus the cost of the pulley and stuff. You'd make around 400-415whp on a stacked setup compared to 350-365 on a standard 65mm. Ask yourself is the extra cash worth the roughly 50-60whp. I went that route so I can't say anything lol. If you can pull it off do it, your 6 will be a monster