Mine turned over like the timing was way advanced, or like it jumped time, I mean it sounded awful.
Also I ran into the problem of it cutting off only when at idle for extended periods, it would run fine and drive fine, no matter what the temp, but idle it with the hood closed, and it did not take long. And it would stumble, and when you gave it gas it would spit back out the intake. NASTY.
I am running without the O2 sensor, which usually affects your mileage more then anything else. I got 20 mpg last time the ZX was out for an extended period of time, in mixed driving, with a turbo trans and 3.90 gears. And while I don't spend a lot of time at full throttle, I still get into boost easily, and even did the ricer flyby on a honda driver who did it to me and thought it was funny. Little did he know, I did not even need full throttle.