I believe the internals are not much good after 400 chp. At 14.7 psi you will be well over that (and then kaboom). Do a dyno (on a mustang) and see if the boost keeps rising then you will know how high you can go.
TE ASA SC, 260/268 TE FI Cams, 38# inj, IK 27, TMS 3.07 finned LSD, F/R subfr reinf, rear cmbr rm reinf, UUC BBK F & R, Ltw fly, Seg kvlr clutch, Sways, Evo III ssk & DSSR, Hawk HPS, H & R C'overs, CDV, P'port SRX, 3M S'guard, MOMO seats, RT cats, Borla cat back, Odyssey 680 battery, Neez Eurocross 18/8.5 /9.5, 245,275 D'lop *spec, Oil nut, Clch stp, gauges, Cstm intake, 131mm pulley, vac. can, catch can & al. r. subfr bushings.