Strange Boost Problem

[SYSTEM6]

hey guys im very new to gtrs and i have just bought an R33 GTR v-spec first things first...u gtr guys were really on to something, and secondly some times after ive been driving around giving it abit here and there but nothing major i will lose a portion (be it half or more) of my boost and it dosnt come back untill i turn my car off for like 10mins and turn it back on, It dosnt do it all the time but enough to annoy me. I have hooked it up to a diagnostic software but it said that there were no electrical problems, then i had a good'n'propper look under the bonnet and i saw that the o2 sensor was unplugged so i plugged it back in and it seemed to be fixed , but just now the problem has come back. Ive researched on here and on the net but couldnt really find anything helpful,

thanx for your time any help much appriciated