I don't think you'll have surge issues. The rpms were full boost will come on will be higher than stock. Even if it did surge at lower rpm at full boost, you would be out of that rpm range to fast to even know you had surge, unless it was a 5th gear pull staring at low rpms. There's alot of 3.0L Supras running twin GT2835's(GT3071) which are a bit larger than what you are considering. Many have done over 800rhwp with them. One I know of with twin 3240's. would say yea, only if you are dead set on twins. If you do upgrade, run atleast 18 psi. No point in running big turbos at low boost.