Tranny vibrates in reverse

I have a 96 corolla dx auto tran. Ever since i put a high flow filter in, i notice the car starts to vibrate when in reverse. Took it to a friend to have it check out. He said that the filter made engine speed run higher and knock reverse gear loose. Don't know if that is the case or not. But than another friend said its bs. Now i check on line and it might be bad motor mounts. I don't know and need help bad.

PS: only vibrates when engine is cold. Vibration goes away after warming up.

Thanks

I have the same problem with a 97 corolla DX, I have a K&N filter in there also.....

Anyone out there?