Re: increase power on alfa 147
Hello and welcome.
No one seems to have attempted to answer your question, so I'll have a go. Firslty, that mustve been a typo in your post - supercharging or turboing your 147 would cost you £3k plus, not £300.
Try a remap, upgraded airbox/filter etc. Will cost you £300ish, but will only add approx 15bhp. Google remap. Angel Tuning are remapping my 2.0 next month.
If you want to add serious power, it will cost you serious money, so you are better off buying a more powerful car to begin with.