Originally Posted by Bamofo
Depends on who tuned it.. In some cases tuners only do it for a small variance of 1-2 psi.... unless they tuned it for stages like 10,15,21 psi then you could hit AFR's that arent desirable as well as too much/too little timing.
Some tuners just set the car to target boost and get the car running correctly there, while the other parts of the table haven't been touched. Lowering the boost could throw you into an untuned region of your map, if so then anything could happen...too much timing, too little timing, too much fuel, too little fuel, etc.
If the car was tuned properly for all conditions up to and including the final target boost, then you'd be fine, but there's no guarantee that it was.