With just a fuel pump and no FMU I would be a bit concerned. You're not doing anything to up the fuel when boost comes on really. An FMU is far from ideal but as long as you don't drive like an idiot you at least have a decent chance of not blowing up your motor.

For the extra reliability, drivability and power that higher flow-rate injectors and a properly tuned Hondata or V-AFC provide, it's definitely worth the price of upgrading. If you can't swing the cash quite quite yet then an FMU is a decent temporary solution but I wouldn't consider it the final setup.