Mine did 20-21 MPG while I lived in West Coast. Ever since I moved to deep south and West TX, the MPG has dropped to 16.6 MPG: Yes, got a lift done but nothing too excessive. City was 12 MPG at best. I then did OEM plug wires, Denso air flow/ratio sensor and O2 sensor and vacuum lines including the vapor feed from charcoal canister with an OEM hose. I think the city MPG has risen to 14 MPG (100% city): Still early to confirm, but that is what I got in last two fill ups.
Generally, you can expect to lose 1 MPG for every inch you lift. It's not set in stone, but it is a rule of thumb. Did change tires sizes and did you re-gear?