Have recently purchased a 1999 2.5 v6 elite with 92500 miles was running fine but has started to make a knocking/tapping noise on idle (very loud) and at revs up to 1500, vauxhall took a stap at piston slap but everybody else diagnosed hydraulic lifters. I had a new set fitted as well as c/belt and tensioners and w/pump. Problem is i still have the noise although not as loud and it comes and goes the warmer it gets i have been told that these engines can suffer from low oil pressure could the oil pump be faulty or the pick up blocked ? has anybody had or heard of this problem before? thought id ask somebody who knows their stuff before i go back to the garage ie you fellows