[Masteryota]

I would start with the head pipe size. That seems to be a pretty drastic step down from the port size, plus you added length, which adds back pressure. An easy experiment would be to try a length of pipe about the same size as the port, and see if it bogs at all. The smaller diameter has an positive effect on low end torque, but prohibits free breathing for the upper RPM range. If you decide to make a new pipe, try to make as few bends as possible, and use wide radius bends if you need to plumb around things. I like CKAU's pipe with the 2 90's and a 45 to put the pipe above the CVT cover, but that may not work for you.

As for the timing, it may be advanced too much and causing issues, but if you are not getting any 'pinging' from the engine under load, you might be ok. Aggressive timing is good for heavily modded engines, but you might need to look into a longer chain. Perhaps Tom will chime in here with words of wisdom.