10 Hot Bolt-OnsLate-model truck and 4x4 engines are impressive performers, exhibiting smooth, useable power characteristics, efficient use of fuel, low emissions, and truly impressive reliability. Much of a late-model engine's stellar performance is the result of computer-controlled fuel and ignition systems. While a carburetor's tuneability and a non-computerized distributor's adjustability are certainly admirable, the confusing myriad of possible fuel and ignition changes is rife with pitfalls. Well-meaning enthusiasts who change a carb's jets and recurve a distributor's spark advance characteristics often find they've actually decreased performance, increased emissions, and hurt driveability. That's not the case with today's sophisticated aftermarket computer chips and controllers. Changes in fuel and ignition are carefully mapped in order to increase performance over what the OE chip offers. And why would we need to change the factory fuel and ignition settings? We're enthusiasts, that's why. We may have installed an airbox, intake manifold, or headers and exhaust, all of which require more fuel and ignition for best results. Also, computer modules can correct speedometer error, firm up an automatic transmission's shifts, and make all kinds of minor tuning upgrades. If you intend to keep your truck's engine bone-stock, you may not need an aftermarket computer chip. However, if you plan any engine mods, a performance chip is a necessary component and will bring out the true power of a modified engine.