have a look down the back of the engine at the tensioner nut and see if you have the z20net tensioner all of the newer chain kits have the net tensioner but then there is a chance that someone just fitted the net tensioner and not done the rest
by taking the rocker cover off you can see if there slack in the chain and if the front rail is damaged thats a sure sign for chaining the chain kits
mk1 = no nicks in the corners of the nut (change full kit asap will have old style oil jet)
mk2 = nicks on the corners (still a good tensioner) if it fails its already to late
mk3 = nicks and nipple on the nut (the latest one with a circlip to stop the end dropping out has a maximum travel limit tho)
left z20net(mk3) -------- right mk2 z22se

if you have the mk2 then chances are its been in there a long time
mine came from the factory with the mk2 and got changed at 55k nearly 10 years 2004 reg