I have standard exhaust minus cat. I modified my exhaust port and flapper when I removed the turbo to put a 12psi actuator on. I thought I'd do both with 1 stone.. When I put my nizpro stg2 plenum, intercooler etc etc on my car, during the night I could NOT get any less than 17psi, and that was with the actuator hooked directly to the boost line on the turbo.. ie, should have been around 11.8 PSI(actuator rating).. During the day, I was getting on average of of 13 psi.. To fix my problem, I put a cat back in. Boost was controled at 12psi again, hot or cold weather.. Since then I have removed my turbo again and opened the wastegate port RIGHT UP, with some guidence from Simon @ nizpro. I originally didnt open it up this much as I was worried the seat would crack being so thin. I have now put my catless exhaust back on the car with no problems. Valve spring problems can be small or big.. if your runnng standard intake / exhaust, you will be able to push boost up, the more you free up the exhaust or intake.. ie, the more power you make, the less boost you'd be able to run. Personally I had no valve spring problems with 14psi.. putting the nizpro kit on I did notice it starting to valve float.. But then again, it shows why nizpros stg 1 kit is, 1) valve springs, 2) injectors, 3) tune.. in my experiance, the standard actuator can only hold approx 11psi up top.. So my suggest would be. valve springs, injectors, and well since you are possibly still going to have overboosting problems, get the wastegate port enlarged and bigger flapper and put a 12psi actuator on at the same time..