Will I need to rejet if I put a K@N filter on my standard DS, and do you think a pipe makes that much difference, any thoughts just how good the standard DS pipe is?

 

The standard DS pipe is VERY restrictive. A pipe will really wake that beast up. Some have just taken the end cap off and modified it so it flows better. That would be the cheap way. Yeah, you will have to rejet. Probably not much, but when you mess with the air flow at all. You have to compensate for fuel.

 

Pipes really wake up the bottom end. A quick cheap alternative, while saving for a new pipe, is to remove the end cap - cut off the baffles - and put it back on. This, with a K&N will amaze you with low end power. Not a real big gain on top, but the low end will be incredibly better. I do recommend the Dynojet kit too - the Needle is much smoother and better on the bottom end as well. You gotta get past the price though - the $50 isn't for whats in the box - its for the R&D that went into the needle design.
Like 02 said - anything you do to airflow will require fuel flow to increase too.

 

if i cut the will i still have enough back pressure?