Problem with my 1.1l punto 55s?

I have a fiat punto 1.1 first car as i ped in january, up to now repairs done to it have been the following since ive owned it (dads a mechanic), new head gasket as i overheated it, new clutch slave cylinder fitted, spark plugs changed and leads. I recently put redex into the fuel system and now my engine rumbles a hell of a lot, and it seems to stall in nuetral a few times but runs perfectly when in gear. Any solutions why? Also clutch seems to click when i press it down? Reasons why? Dont tell me i need a new car because to be honest i cant afford one in this current economic climate. Cheers