Hello, my name is Mark and I will try help you with this.
It is very unlikely that the slight oil leak is causing the engine management light to come on.
What you need to do is have a scan tool connect to the car and read what fault codes have been stored.
The fault code will give an indication as to what is causing the engine to run lumpy.
It could be a few different things, not just the injectors that would cause these symptoms.
Why the poor service rating?