That's absolutely terrible mileage for the performance and power. Both the Z4 coupe and 350z get better mileage than the crossfire with better power and performance.

To the OP- If you want a something that's got some real get-up-and-go, I would listen to the others and get an SRT6 or another car with relation to your intended swap idea. That blown 4-cyl Benz motor is a turd. I'd rather swap in a VW/audi 2.0t with a big turbo kit from APR, if you felt the need to go with a 4-cyl FI motor (despite all the custom stuff that would need to be done). Though, in my mind if I was doing a swap on a crossfire, I'd do it right or not at all. I'd fit the burliest M-B V8 I could afford in the crossfire. THAT would be a motor option worthy of the design of the car! I know there is at least one of member here that has done this.