it really depends on if there is anything else wrong with it.... i would start with the CEL, take it up to autozone, they scan them for free, and see what codes you are getting... it could be just pointing to the ECU/key issue... but there could be other things going on as well.... thats just my personal though

 

If the key thing doesnt work check for a plugged catalytic converter that will keep u limited to about 40 45 mph

 

Also the gas consumption is horrendous and when you lightly tap the gas the rpms shoot up but the car isn't really moving that quickly

 

Really, get the CEL checked first, then worry about all the rest