I havent done a timing belt on these yet myself so dont know from experience but I beleive there is more then 1 part to the tensioner. I recall reading some posts on other sites about a knock still being there after changing the tensioner but they didnt change all of it.
Check the forums at www.planetisuzoo.com
and the rodeo section of www.automotiveforums.com
and do searches for "timing belt tensioner knock" should have lots of info.
If you let your engine run really low on oil then it could very well be a rod knock. Usually the #1 cylinder since it gets the oil last so has the lowest pressure.