The engine makes a screeching noise seems a loose ac belt it seems the belt can only b replaced and not tightened. The dealership cleaned it once n the noise did not stop second time the lubricated the Idler of the timing belt still there is this noise. It is pronounced upon switching on the AC.

Switching on the AC will mean more stress for the belt as it now needs to drive the compressor. If there is no sign of wear on the pullies then a replacement will be the only option. Once it slips it starts to wear the belt and the roughish surface thats used to help it grip is worn away.

The engine code in my octavia Vrs 1.8t is AUM and the rated HP is 150 bhp could anyone tell me what turbo charger is installed and what type of remapping( i.e phase I, II etc) should I go for without major modifications to either the turbo or the engine and what max power and torque can I achieve??

Welcome to the forum.

Your question would be better posted elsewhere to get the best response as this is the 'Say Hello' area!.

I ve finally changed the alternator belt and lubricated the belt tensioner but the noise is even more pronounced now. I think the problem is elsewhere.

Did you ever get this problem sorted out as i have the same prob and am about to change auxillary drive belt?

List of possibilities (as I think of them) if you've eliminated the aux drive belt:-

1) A/c clutch slipping.

2) A/c compressor bolt about to fall off. If so, fix it quick as it's 5 mins with a spanner or £Lots for a new pump!

3) Problem with clutch, probably in the thrust bearing. This is most likely if you get noise when changing gear.

I had my car taken to the workshop about 5 times and then at last the Idler pulley of the Alternator belt was changed which stopped the 'CHICK CHICK' noise however after about 4-5 months I suspect the noise has started again but its very low right now.