Bit of advice needed asap please!

[HiTower]

I recently had a new custom exhaust fitted from the cat back. It's 2.5 inch with a 4 inch tailpipe with only a back box. The problems I've had is I don't think I'm getting enough back pressure for the car as the turbo isn't spooling up as much and there is major burbling/popping. I've looked at other exhaust systems and they all have small middle boxes and wondered if any once else had had problems like this and if fitting a small middle box may cure the problem? Cheers guys :-)

[Glanza_cl]

if you don't think you are creating enough back pressure just sort out the breathing the more air flow getting to the turbo will help the spool time, if the exhaust is a lot less restrictive it will be venting a lot more gases so just front mount your filter, decat ect and it will even out and be fine. but if you are not happy with the exhaust talk to them you paid for it so tell them what you want done and they should sort it.