Originally Posted by grandpawmoses

If, after the exhaust and intake mods, everything seems to run okay, there is a cheap way to tell if you're running too lean. Warm up the car, Run it hard for about a mile, shut it down & coast to a safe stop, immediately remove a spark plug and check its' insulator color. Black is too rich, white is too lean, and tan is what you want to see. If it's white, get it tuned immediately.

For what it's worth
Not to justify the cost of a tune but it involves a lot more than just getting the air/fuel ratio to a stoich AFR(about 12.7 AFR for 91+ octane fuel in a naturally aspirated engine). It also involves timing, spark knock retarding, cold cranking enrichment, acceleration enrichment, and deceleration enleanment to name a few. The AFR is adjusted for each cell in a table of throttle positions against engine RPM's. This is done for each cylinder too. The dyno technician really needs to know his stuff and will still take over a dozen wide open throttle runs even with todays computer assisted tuning software. Also, get a copy of the tune or "map" on a thumb drive & keep it. It'll save you some money if you ever need to reflash your ECU.