Depending on agreement with partner I play either OGUST or 2N asking for feature over weak 2 openings. Hence when partner forces with a new suit, I would tend to support with 3 cards in partner's suit. With no support, I would bid an outside A or K if I had one -- rebidding my suit would deny an outside A or K and deny support for partner. The only time I would bid 3N is when my own suit is headed by AKQ.