The boost bottle on mine made my engine run smooth especially in the bottom end but it did nothing as far as performance so it's not really a performance mod.
You say it really starts to pull up top. That power band if it happens sooner would make it feel like it's pulling stronger would it?
Here's what I recommend. Either get a 40 tooth so you'll get better bottom end but yes you will lose top end OR get Ghost0's shifter kit.

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