have a 99 xk8 that i just replaced the knock sensors on . things have been fine for 3 months or so but am now getting a random restricted performance light and a code stating low voltage on bank one on the knock sensor . seems to occur when i get above 2300 rpm or so then goes away when i get at around 1500 rpm ..any thoughts ...am suspecting a fouled plug and was going to replace them all in the near future anyhow. car seems to be running fine but there may be a slight stumble at higher rpms . thanks for any input .