One of the most common queries I get is What should I do first?. There are so many BMW performance options out there and some upgrades are not going to give you the end result you want. It is important that you choose wisely, buy excellent quality parts, and install them correctly.
For most late model BMW's, the greatest horsepower gain per dollar is through a software upgrade. There are a whole host of retailers out there who offer software downloads to increase power and torque and also usually remove the top speed limiter and raise the rpm limit. For BMW's manufactured after 1996 in the USA this is very important. Until the software is modified, an cold air intake or performance muffler will not result in any increases.
After the performance software upgrade, then I would recommend a BMW air intake to get more oxygen and cooler oxygen into the engine. These are usually fairly simple to install.
Once these steps are finished, then buy a performance exhaust. This will result in less back pressure, more horsepower and a more aggressive exhaust note. Brands like UUC, Remus, and Borla are highly recommended BMW choices and can be purchased at most BMW parts specialists. Do some research to ensure you are purchasing from a manufacturer that is able to give you the best advice for your specific model of car. Buying the right part the first time, before you install it, will ensure yo get the hp gains you want.
Each of these modifications is easily reversible and will increase the driving enjoyment of your car. Please ensure you obey the local and state laws where you reside for modifying your car.
Rand Stuck is a master technician with over 7 years experience working on BMW's and currently manages the BMW parts department for a large BMW dealer.