Porting does create a problem !! I remember when porting was first becoming popular and a cop friend had his 357 ported .He was very happy until one night he fired in the dark - he sold it immediately !
But muzzle flash has nothing to do with the make of the gun !! It's a powder problem primarily. Made worse by shorter barrels, higher pressure loads [357 vs 38 spec] Newer powders have more supression of muzzle blast and flash through powder additives.
Check different powders ,use longer barrels ,6" instead of 4", use 38 spec +P instead of 357.