driving > mods as far as improvement goes. instrumentation helps a LOT also. if you have an obd2 vehicle(96+ in the US) you can get an obd2 bluetooth adapter DIRT CHEAP that will link to a smart phone and tell you a great deal of info on your vehicle. its a good start
adapter:
Amazon.com: mini small v1.5 Bluetooth Mini Small Interface OBD2 Scanner Adapter Torque Android: Automotive
Smart phone app:
https://play.google.com/store/apps/d...l.torque&hl=en