Hi all, Need help with a problem with my 05 VZ V6 Alloytec. Just had timing chain and guides replaced and now I have no oil pressure. No oil seems to be getting to top of motor. Been at the mechanics for 2 months and they can't find the problem. The pick up works ok. Pump is ok. Lifters are ok. When started it will run ok but then a loud tapping at the top starts. It then runs like ****. Any thoughts?????