I had the same question today and got it answered by Dave Dalke.
It's all relative!!!!!
Let's see, if you have the MPII blower, and all the goodies, and no tune....The book is already written up on you because you are probably running WAY TOO LEAN!!!! I proved this today because the dyno tune I did proved a 13.7-1 ratio that I thought was good from a previous tune. First things first, get a tune......
Second....If you are running 5%, what boost pressures are you seeing. I don't mean at 3000 rpm, I mean at 5000 rpm in a higher gear....12-15PSI????? If this is the case, leave it alone, MPII's don't tolerate the higher speeds that MPIII's will.
I have a stock bottom end, stock heads, medium lift cam, exhaust and all the goodies. I ran 17PSI at 5500RPM
This is considered high. It only saw 12 PSI until about 4500 RPM then up went the boost pressures. This was with an MPIII. This was also with 15% overdrive.
Needless to say, without a tune and some more info, no one can honestly answer the question.
As always, I am always available. Give me a call and I will help you with any questions you may have that I can honestly answer.
Don
(973) 277-4294