New 05 mini S owner here thinking of doing 1st mods.

I have been reading that the 15% pulley is the most popular to start. So do I just purchase the pulley, install and voilà! or do I need more components to go with it. If so what are they? I have seen here mention of intake, new spark plugs but do not understand if they are absolutely necessary and why.
Also, which brands are best bang for the buck quality and price wise. Also thinking of the one ball exhaust mod.

Thanks in advance!

 

you should post this in the gen 1 forum

 

My apologies. Didn't notice I was in the wrong section.