Hi, I have two vehicles a 1999 Oldsmobile Alero 3.4L v6 and a 2015 Hyundai Genesis Sedan 3.8L v6.My Alero started running poorly right after changing the oil. It sounded like a valve was sticking (it has 204K miles). So, I purchased your Product 2611-Pro and followed the directions. It worked perfectly and the valve no longer sticks, has smoother and better performance. So, I bought another box of 2611-Pro to use on my Genesis. It has a valve that is "tapping" after it warms up. So, I wanted try it to see if it would clean the valve deposits like it did on the AleroUnfortunately, the product didn\'t have any effect on the Genesis. An interesting thing that happened is the smoke that came out the Alero was a lot when I drove it as directed. What came out my Genesis, was one \'puff\' of smoke, nothing like the Alero. The difference between the two is the location of the Mass Airflow Sensor. On the Alero, it is located close to the air filter box. On the Genesis, it is located close to the air intake header system. So, I had to let the 2611 cleaner pass through the MAS on the Genesis. I also had to turn around the yellow plastic tube to get it to fit under the air duct collar and not be a problem. I followed the exact same procedure that I did for the Alero, but there was no difference after using it on my Genesis and I am wondering why? NOTE: I did add your fuel additive to both vehicles that I poured into the fuel tank.So my questions: 1. Why did the Alero smoke a huge blob after following the process, where the Genesis just did one little puff? 2. Is there a difference using it before or after the MAS? How could I have done it differently? 3. Is there a better product that I can use to try and de-carbonize my valves in my Genesis? It has a GDI. Should I try another can of 2611? I have pictures on how I did the setup on both vehicles if you want them. Thank you for any help you can provide for my Hyundai Genesis. Dan CherkasDeer Creek, MN218-371-5816