boost hesitation

Here is the problem. Everytime I run somewhere between 15 and 18 psi my car seems to have hesitant serges.... I ordered a set of iridium plugs (1 step cooler over stock because I couldn't find 2 steps cooler). At the same time this happens I run slightly(slighty) "less" rich. (I would have said leaner but thats implying it's running lean in the first place but its not....)
I need to install my wideband I guess.... Retune the fuel pressure, and maybe the timing. I guess it may even be the octane... 93 is great but 16 psi of boost is a bit of final compression....(approx. 15.66 to 1) and the threshold of 93 being 15 to 1 fcr........