What is the most cost efficient way of improving performance for Honda Accord 2007
 

4cyl? Performance Chip?

I wouldn't. I think that really stresses the engine. It's not what it was designed for. If it's a performance you're looking for, buy a performance car.

i've said it before--perf chips cause the engine to think it is something it isn't. the increase causes premature failure as the original chip is for the engine parameters. your mileage will reduce, your maintenance will increase and your warranty will cease after installation. oh yeah--when you change the chip the "black box" will maintain a record so you can't cheat. stay with the original.