Low MPG on E39 530i. DISA Valve?

I am getting around 15 - 16 mpg on my E39 530i with almost all city driving. Fuel economy has dropped almost 3 MPG over the last few months.

I noticed the car is running rich, with a heavy gas smell on start up. No check engine lights are on, so I am wondering if it's the DISA valve.

I swapped out the old DISA valve with an off-brand bought on Amazon. The build quality is similar to OEM, and the price almost identical to rebuild kits. I will report on the new DISA, as time goes on. Hopefully, my low MPGs are resolved.

I could tell an immediate improvement and idle. It also seemed like the 530i has more power, and isn't downshifting as much.

I figured my DISA was failing due to the rattling noise around 3500 rpm. I took removed the old DISA and there were no missing or broken parts, and the seal looked fine. I changed it out anyways.

Here are the things I have changed, that could change MPGs:

• OEM spark plugs
• Brand new valve cover gasket and seal
• Air filter
• VANOS seals
• Pre-Cat 02 sensors
• Intake and Exhaust VANOS sensors
• Pulleys, tensioners, and accessory belts
• Cleaned MAF, throttle body, and ICV
• Fuel Filter
• Oil changed every 5,000 miles
• Upper and lower intake boots
• All vacuum lines 

The other items that need to be changed:

• CCV
• Post Cat sensors
• Throttle body gasket
• Coils
• MAF
• Injectors and o-rings
• Intake manifold gaskets

I can't think of anything else. Does the fuel pump affect MPG?