Do I have to purchase an after market computer to assist or replace the stock fuel injection computer if I only change my pipes?”
No. Changing only the exhaust on your fuel injected Vulcan does ‘not’ require an after market computer. This isn’t because the bikes FI computer adjusts for the difference…it doesn’t. Just that the intake is so restrictive that you have the equivalent of drawing air in through a straw and exhausting it through a sewer pipe. Until you enlarge that straw you’re not going to see any appreciable difference in the amount of air being drawn into cylinders so no need to add fuel. It is highly recommended, however, that you check your spark plugs after changing pipes and riding to be sure you’re not running lean. There are some pipes available (drag pipes would be an example) with little or no back pressure. In this case an after market computer might be advisable. Changing your intake is a slightly different story and (on FI bikes) an aftermarket fuel module is suggested to make the engine run its best. This can be a good thing. Several models are available and most allow adjusting mixture
