If its the altinator belt, it will squeek only when you pull away. Without hearing it and looking its hard to offer any help.
the easiest and cheapest way to improve power on a car is to free up the breathing i.e Intake and exhaust. Other than forced induction (turbo/compressor) I dont know of any better intake for the almera than a pannel filter (K&N). Other than the manifold the exhaust ahs been replaced for an after market.
the de cat will make a difference but it wont be major, same with any other mod you want to do from here on out. That is why I didn't do anything else, lots of money for little gains.
If I were to do anything I would replace the exaust manifold
Good to hear it Wspoons gets busy on a sat.
Hey we ain't no spud pickers