A common problem the Mk4 12v VR6 motors suffered from is a faulty intake manifold shift rod. This usually caused a flapping / rattling noise from 2500 to 4000 RPM in the power band usually due to the bushings being worn out. This is a new OEM part to replace your worn out unit.
2.8L 12 V VR6 ENGINE - with AFP Engine Code (99-02 Golf/Jetta VR6)
⚠️CALIFORNIA WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov