Broom yellow is very hard to match paint if you're thinking of re-spraying it. I'd reccomend trying Autoglym Paint Renovator or T-cutting and some good quality polish if you haven't already
DONT use a burnisher on plastic bumper ect,try t-cut by hand but you will never get true colour [as plastics different from metal painting]..or t-cut and use that nasty colour magic[NNNNNNNNNNNNOOOOOOOOOO],
Use cutting compound like G3 by 3m as la rossa mentioned, it really brings the colour back on red and white cars so I dont see why not on yellow!
I have a broom yellow punto too and it's annoying to get the colour to match exactly, if you were to spray something, then you'd have to leave it a few weeks to settle in then use some rubbing compound to even the colour out a bit!