Hey guys! Just bought a 2006 Zx6R with 33k miles on it. After her dying on me TWICE, I finally parked her in the garage and did a little work. Long story short, she needed a new Magneto. I now have a problem that I can’t diagnose myself, so I’m looking for you beautiful people’s help

In first and second gear especially, the bike seems to have trouble getting past 8,500 RPMs. If I give it more throttle, the bike will redline in both gears, so I don’t think it’s a fuel issue. If I cruise at 8,500-9,500 in these gears, I can hear a somewhat hissing sound. I’m not sure how to describe the sound, but hissing is the closest to it. My bike also pops A LOT when engine braking, as well as engine braking very harshly. (My old bike, a 2003 Gsxr 600, didn’t engine brake nearly as hard.) Yes, I rev match when downshifting. Yes, I know it has a slipper clutch. My guess is there’s an exhaust leak, and I believe it’s coming from my headers. (The sound is in that general area.) I’m also suspecting I could need a new valve cover gasket/head gasket. Am I on the right track to solving the problem? How would I go about troubleshooting? I could buy the gaskets and replace them, but I don’t want to blindly replace parts without knowing why and if they’re even the culprits. Thanks!

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