Things you learn as you go along:
If you take an ordinary car and fit it with headers and a less restrictive exhaust system, like the previous owner did to my Camaro, the sensors in that system will report slightly different data to the computer, which causes the computer to panic and demand that you take the car in for therapy. Turns out this is a well known problem and the solution is a professional mental adjustment to the computer. Resist the temptation to do this yourself with a ball pien hammer, and take your car to a reputable speed shop.
I took mine to J&S Performance and Tuning and the folks there knew exactly what to do. Download the software in the ECU, revise a couple of numbers, and load it back in. The car now runs smooth as glass and the dashboard remains free of "service engine soon" lights. For a significantly larger fee they could also get me about 10% more horsepower, but considering where I'm starting from we both agreed it probably wasn't worth it. OTOH, if you drive a GM car and are frustrated that it's producing less than a respectable 450 hp, these folks can help. I looked over some of the cars in their shop and believe me, 450 hp is strictly for the economy cars.