Question: Midichlorian's are chemical compounds found within every living cell that forms the basis between the connection life and the Force. Without midichlorians, life would be impossible. The amount of midichlorians in a life form represents its ability to understand, comprehend, and manipulate the Force.

My name is Darth Incognitus, and I have decided to absorb more of these cells into my own body to make my force sensitive abilities stronger. To accomplish this, I have kidnapped numerous force sensitive users who match my blood type. When their midichlorian count has been measured, I will perform a blood transfusion from them to myself in order to absorb these cells. After I have attained enough of these cells, I will become the most powerful force user in the world and create my Sith empire. Then, I will use this method to strengthen my apprentices and students.

However, after a number of tries, I have noticed that my powers have not increased. No matter how many Jedi I murder and drain of blood, my abilities remain average. Why would this be the case?

Answer: 
Obviously blood can only contain a certain density of midichlorians or it would clog up and ultimately become solid. Your body will naturally break down any excess of midichlorians and convert them into fat. This is what happened to Jabba the Hutt.
Midichlorian's are not the bottleneck in this equation. Your body and brain have developed "Force pathways" to make use of the amount of Midichlorian's you naturally have in your blood. They finished developing at the age of 16. You can add all the chemicals you want to your blood now, but your body and brain simply can't use them for anything--they can't handle that much Force.

Now if you'd started these transfusions before you turned 16 and your body finished developing it's Force pathways though... Have you thought about creating a test experiment heir to your power?