This is for the V-8's. When I first got my Lotus the valve noise cold was bad. It would go away but it took a while till after it warmed up and the lifters pumped back up. I did some oil changes hoping it would clean the lifters and improve but it did not. Finally, just before an oil change I used an oil flush additive and ran the motor a short while on it. Did the oil change and now I hardly hear any lifter noise even when cold. This advice will NOT help anyone with a 4 cylinder motor, the lifters are NOT hydraulic, self-adjusting. Valve noise on them can only be stopped by manually adjusting them. Valve noise and exhaust leaks can be tricky, one can sound like the other or maybe you have both! The thing to do is check your valve clearances and if the noise is still there you may have exhaust leaks. It can't hurt to check the valve clearances first and should be done regularly anyway. If you do have to adjust clearances be sure to inspect the valve caps. There have been reported instances of fatigue on them here on this forum.