Horrible MPG/Fuel odor troubleshoot

My Duster once was getting 8 miles to the gallon (on the freeway). And the exhaust smelled terrible.
Come to find out my Carter fuel pump (M6270) was putting out too much pressure (about 8 psi) and one of the brass floats in the 650 AVS developed a leak which filled up with fuel. Therefore causing a very rich condition. I Replaced the brass floats and installed a regulator and set it to 5.5 psi. I was getting 13.5 on the freeway (woot!)... Wait... What's this, why do I have green/yellow deposits on three of my spark plug on the passenger side... Doh! Yep blown head gasket... Darn! Replaced that as well and new sparkplugs.
Now I'm getting around 17 mpg on the freeway on a warm day and about 15 -15.5 mpg when its about 35 degrees outside. (darn airgap).
Sorry for my little story, but my point is: it can be a combination of things. (hopefully not your case) It can be frustrating to "find" more issues when you're not meaning to.

By the way what kind of fuel pump do you have?