Actually with the variable cam timing and all the other programmable features on today's engines it is possible to gain in HP Torque, and Fuel Economy without any sacrifice in idle quality. However, it's still true that there is no free lunch.

The factory programming is designed to provide a reserve in terms of emissions to assure compliance at 100K or more miles. These modified programs don't have that reserve capacity in them and in some cases may cause the vehicle to exceed the emissions standards for it's model year even when the engine is still factory fresh. For most this may not be a concern, however in some areas there are mobile sniffer trucks prowling the streets and getting caught with a non certified chip in place will carry a very hefty fine.

Rule One, make sure that any chip you purchase is certified for compliance with your vehicle AND your model year. Close is only good with horseshoes and hand grenades and having a chip certified for a year earlier that what you are driving can add up to a serious fine.

Second, playing around with the shift points and transmission pressure levels will most likely void the warranty on the transmission. Today's transmissiion are rather borderline and they won't tolerate much tinkering with the factory control settings. The factories put in huge numbers of hours in testing to determine what control settings will extend the service life as much as possible. Basically, in terms of ruggedness, today's transmission are barely a shadow of the old Torqueflite 727 or THD400 that could last 1/2 million miles without any service, they are designed to be "low drag", light weight, and have a service life of only 150 to 200K miles in stone stock configuration. Tinker too much with the factory control maps and the service life will plummet. In addition, a major boost in horsepower will most likely result in a transmission that slips at each shift, which reallly tears up the cluches and bands. The answer to this is usually to boost the operating pressure, which then degrades fuel economy and also increases the failure rate of the "hard" components such as the gears, housings, and shafts. Basically, add 200 hp to your engine and you can expect to be purchasing new transmissions at rather frequent intervals.