Noise

I took my Mk1 for its MOT last week and heard a metallic contact noise while on the way. The test centre couldn't find the source but reckoned it was between the intake manifold and the block (not sure if that was mechanic humor). That said, the noise gets louder when I booted it and even worse when I let off, which indicates gearbox to me? Any thoughts? It's a 1.8 GTi cab, E reg. the gearbox was rebuilt, badly (accordingly to the previous owner), so I'm leaning towards that. I don't remember it happens when the car's stationary, i.e. not in gear.

sorry but not much hope of helping with what there is to go on.

when you say a mettalic contact noise is that a tapping noise or a rattle noise or a grinding noise

really need more details, did it suddenly start to make a noise, can you feel anything in the cab?

intake manifold bolts to the head but the exhaust is underneath it?

Have you checked the C Clips holding the exhaust to the manifold ? Heatshield, all driveshaft bolts secure  ?

It's a grinding noise. The test centre checked the heat shields. I've not checked anything personally. I've driven the car no more than 20 minutes since I bought it as I've been working on it most of the time, so couldn't say when it started. I'll check the bolts when I'm next round there.