‘91 coupe poor fuel mileage

[Christopher Gharibo]

I would like to thank the list in helping me solve the start up, idle and driveability problems of my CQ. The culprits were a bad MAF gasket, dirty MAF, dirty ISV and a bad reference sensor. The car drives extremely well now. I just love this car. 

What I am still experiencing is crappy mileage. I used to get 350 miles per tank which is now down to 280 - 300 miles. 

There is no fuel smell or leak of any kind. There are no codes. The spark plugs look dry and normal. Exhaust is barely visible. The injectors are almost new. 

What can cause such a drastic drop in mpg and where is the fuel going?

Thank you for all the advice. 

CG