I just ordered a MEVI for my 97 SE, do I have to worry about detonation? Should I get colder spark plugs? Also, should I get a S-AFC, or an ecu upgrade? I already have y-pipe/cat/catack, air intake, and UR pulley. If someone would clear this up for me I would really appreciate it, thanks.

 

No to all (except the ECU...see below).

The ECU isn't absolutely necessary, but it would be a good idea. The mevi loses alot of low end power. The ECU will make up for much of this. You can also get a raised rev limiter. With a stock IM you would have to reason to go past the stock redline, but with the MEVI there is still quite a bit of power up there.

What year is your car?

 

If you want your car to be significantly faster, get an ecu with a raised rev limiter. The rest of your questions can be answered with the word "no".