maybe your car is not running 100%. well if you got corolla inlet mani and filter it could that your car is running lean, when the speed picks up it means it will be running ultra lean.this means the mods you got are not being used to full peformance. check your spark plugs is they covered powdery stuff then you need some more fuel going in. a lot of N/A boys forget this and this is why the mods don't seem to be doing the job.