I was reading someones post about their 1988 dommie and he/she mentioned that the '88 dommies had restrictors in the header pipes. What do these consist of, I'd assume something similar to carb restrictors, and most importantly, how do I relieve myself of them?

I have removed the airbox to add a bit of preload to the shock and noticed that when I look into the open end of the carb and twist the throttle wide open, the slide only goes half way up...is this correct because I'd assume it would pretty much disappear into the top part of the carb? There is quite a lot of free play in the twist grip so I guess this doesn't help the matter

Cheers fellow Dommie lovers!!