Port injected fuel system means the fuel injector would spray into the intake manifold or port. The fuel would mix with the air and travel into the combustion chamber once the intake valve opened. With GDI, the fuel no longer moves over the intake valves. This is not a bad thing except, the intake valves are no longer being “Cleaned” by the passing fuel. Here’s the maintenance part. Over time the intake valves will develop deposits. These deposits could get to the point where the valves no longer seat properly, developing poor engine performance.
Deposits are normal for any engine. It doesn’t matter if you change your oil and air filter once a week. Now…… please do not take that the wrong way. You need to change your oil and filters on regular intervals,but with the onset of GDI engines we need to add a service that will keep the intake valves from gathering to many deposits.