Fan belt and Light exhaust mods

Did a long journey afew days ago, Was speeding up a hill when I heard a sudden thwart from the engine almost thought the block had cracked or something, I crossed my finger and drove on for a few kilometres when, I slowed down to enter a junction the steering felt like it had hiccups and had a loosy feel, i immediately stopped to inspect the engine and half of the alternator and power steering fan belt looked like it'd taken a blow and was gone with the remaining beaten half still holding on, I managed to get a replacement belt and when I got back to civilisation I went to my dealer and got both belts replaced, since then I can her a belt whinning when i start the car, when I'm driving slow my legacy bp5 is a maual, I also noticed when going uphill especially coming from a dead stop the car stutters from lack of power and goes off, have to go back down the hill and start off at a higher speed to negotiate the hill, so my questions are

- how can I fix and or tighten the belt for it to stop making the whinning noise?

- why the car looses power uphill and what's the solution (changed plugs)?

Apart from the sound system the car is fully stock! I would like ideas on any light and not so pricy mods I can perform on the car... Currently I am satisfied with its performance and would just like suggestions on what I can do to get the oldies subaru roar and bubbling nothing loud jus something even my wife can appreciate

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