The job the rack bushes do it's not going to be subject to anything untoward vibration wise, esp after going through several other bits before the steering wheel, they wouldn't imo cause anything that stands out vibration wise either through the car or at the wheel.
tabetha
ps I've fitted some but not driven them yet, the old ones are dead easy to get out, if engine is in the car use a long bolt/studding and socket to pull them through, if engine not in car, just use a drift and knock out downwards.
tabetha