Dougs951S

Not at all, I've already logged over 36 lbs/min of air and that wasnt even at max boost, something around 1 bar on a little k27. At 1.6 bar with a great flowing head and intake and a monster holset, I think it will get there. I dont know how much I'm putting down right now, but I can tell you with an LSD and wide, sticky tires I can shred them from a roll in 2nd. I havnt datalogged airflow at higher boost but I'm currently at 22 psi and probably 360+ rwhp. Loads of people have made +- 400 rwhp on the stock downpipe with way less mods than my car has. By the way, the pressure drop between the turbine and the downpipe is only about 2 psi more with a 3" vs a stock pipe. Its definitely a restriction but I don't think it will be that detrimental.

Edit: Has anyone ever measured the exhaust velocity coming out of a stock downpipe under full boost? According to rough math, in order to reach 600 cfm out the 2.25" DP the velocity would need to be in the range of 360 ft/s. For a 2.85" ID pipe, that drops to around 225 ft/s, which is actually a significant difference.
At a flow rate of 525 cfm which I have already logged, a stock DP needs to hit ~315 ft/s. A 2.85" pipe needs only 200. So it appears I may have initially underestimated the restriction the stock pipe poses. My previous comments still stand.

Double edit: 400 rwhp is probably more reasonable, math puts a constraint on me reaching 425 with this setup purely based on the amount of boost I would have to run. I don't doubt for one second that that is achievable.