the thing is with engine mounts is that they are designed to absorb the engine vibration and the rubber is "tuned" to do that. swapping to poly bushes does away with everything that was done in the development stages so you will then get all the vibration given out from the engine when running. As you have found this vibration is felt in the pedals/dashboard and you should aslo feel it in the steering wheel and seat. Altering the torque on the bolt will not help much and leaving it slightly nipped up could cause it to vibrate loose. the only rela way to reduce this vibration and be the same as it was is to go back to the std rubber bushes, not sure if they poly ones can be pushed out and a set of std ones inserted