Digital BW, The Print

I found people in this group are very knowledgeable on MIS products. 
So I'd like to ask your advice on the problem I experienced when use 
MIS GP black ink. I ordered the GP ink cartridge for my epson 1280 
recently. I got good results on matt paper but had bad results when 
printing on glossy paper (epson premium glossy, luster and permajet 
oyster paper). On those glossy-based prints, when I tilt the print, I 
can see the reflection of the black portions are so odd that they 
dont' seem to be part of the print. In other words, all other colors 
are melted naturally into the paper but the black portions are like 
something that are separately patched on and not the integral to the 
whole print. I was wondering if this is so called "solarizing 
effect". Any of you have used MIS GP inks? What are your 
experiences, particularly for printing on glossy paper? MIS claims 
that the black ink in the cartridge is Universal Black that works on 
both glossy and matte. But my result is clearly unsatisfactory. 
Should I use their Photo Black (PK) instead? If so, will I have good 
results for matte printing?

Thanks.