94 vx only getting 25 mpg!?!

[rsport]

ok, i am new to the site here. and i am hoping for a miracle with the guru's here.
i bought a 94 vx las october knowing that it was going to be a project. but the guy didnt disclose all the problems the car has so now i am in it further than i thought i would be.
i have fixed alot of the cosmetic and critical problems with the car. she starts right up, feels very strong, does not smoke, tranny is smooth, handles very well, and sounds great. except i am only getting 25 mpg. 90% of my driving is city stop and go, about 20 miles/ day.

things i have done so far.
new oem spark plugs, correct gap.
new fuel filter.
fresh oil and oil filter.
new air intake with new filter.
new tires, with lightweight rims.
alignment
DC sport headers, custom 2.5 inch exhaust
lowered 3 inches.
vx transmission with new clutch.
new battery

other issues:
the CEL comes on at 45 mph.
the speedo does not work right.

I just ordered the 5 wire O2 sensor for it.

I think i might need to do a timing adjustment and valve adjustment.

I would greatly appreciate any help. thanks for your time.