SR4A includes the limit, I believe on page 199, but I'm away from my book. There is no limit, that I remember seeing on an individual focus' rating, but the total rating is limited to magic x 5. So after character generation, a character could technically get/create and bond a rating 30 weapon focus. Now, I have no idea what the actual odds are of creating or finding something that obscene.
Note that you should not exeed a total rating of magic x 2 if you want to avoid the risk of focus Addiction.
QUOTE
The gamemaster can call for a Focus Addiction Test at any time she feels the player is abusing foci; a good guideline is whenever a character has a total Force of active foci in excess of twice their Magic attribute. When a character fails the Focus Addiction Test, she gains the Focus Addiction Negative Quality
(Digital Grimoire p. 8 )To most GMs, using a level 30 focus is where "feels the player is abusing foci" will apply.
