I recently went catless on my 17 m6. I had vmp do a tune revision for it and it feels like I gained more hp. I also did a 2 dyno pulls back to back and put down 440/390. Car does feel like it has more pull to it. I do not have headers. But i have a xpipe pmas and 18 mani.
I currently use vmp for my tuner. They are great and fast. I just recently took it to the dyno and put down 440/380. 2017 m6, cat delete, pmas, 2018 intake manifold.
I am thinking about giving lund at shot. After my lth install.
I have used 5star in the past for my 3.5eb and didn't have any...