Oil in fuel on isx 600

I've got a 2001 ISX 600 that is getting oil in the fuel and I'm trying to figure out where it could be coming from. On these motors the fuel pressure runs so high after the high pressure pump that it seems it'd be more likely to get fuel in my oil. Has anyone ever had this problem? The only place i know that oil is close to fuel at low pressure is at the high pressure pump.

 

We had that problem when I first got the truck it had set for a few months and we treated the fuel a few times but couldn't get it so we drained both tanks and used acid to clean them then put in new fuel and in about 1 week it was already blackened and has continued to get worse. We also replaced all suction and return lines so they shouldn't be any problem. Got a new gasket for behind the high pressure pump that we are going to replace on monday. I've read some about the cooked fuel but didn't think it would happen this quick? Will post what we see Monday when we take pump off. Thank you all for your imput!

 

Im hoping this is the problem. Pump was replaced about 3 months ago do you think we may have gotten a faulty pump? We will know more after Monday. Thanks