Reducing speed will probably be the most important, ie. highest percentage improvement. Try following what Moorcomp said. The vacuum leak thing is a more advanced thing, but it has been very effective for me.
Now go outside and pull that knock sensor. I've had mine pulled for years with only side effect being Joy!
There are some cheap to free performance mods on teamzx2, you can do them and not suffer any mpg loss and you will gain some driving pleasure.
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