Bridge PU vibration

I put a set of SD Blackouts in my guitar. At band volume levels I'm getting feedback unlike any I have experienced before. The bridge pickup vibrates during this feedback and I can stop the feedback by putting a little pressure on the pickup with my fingers. I have tried turning down the gain and the level on my pedals and amp. I have tried putting some foam padding in the cavity under the pickup in the hope that it would help stabilize the pickup. I have added a second spring on each side of the pickup. I have run out of ideas and I don't really want to go back to the old pickups.

Any thoughts?

Try rubber tubing instead of springs. It can help a little, though I've really experienced the level of vibration you are describing.

One more thing, is this pup mounted in a PG or pickup rings Make sure those are mounted securely as well. Sometimes those screws strip out ( even if the screw is in there it may not be holding it down well) and the ring or PG will be vibrating as well..

Thanks for the reply.

I noticed it is only on the treble side. There are no stripped screws, fortunately. I will see if I can find some rubber tubing.

You want something like the following. It's essentially thin surgical tubing.

http://www.stewmac.com/shop/Hardware,_parts/Electric_guitar:_Screws_springs/Pickup_Spring_Tubing.html

I was hoping to find some locally and not have to order some. I'm going to talk to the guys at work tomorrow and see if they have any. I'm on friendly terms with the janitor and he usually has a little bit everything stashed somewhere.

I'd go that route too. I just posted the link incase there was any confusion on what I meant, and as a last resort. Some craft stores have weird stuff like that too.