shame it's not a turbo - Van Aaken sorted my 1.9td 19 (same engine) and it flew - 93 to 110bhp
BUT:
1) performance air filter - a K&N helped my 1.9 breathe a lot better - £30 ish
2) weight - just 50kg would make a difference. Without ripping everything out, you can:
Lift our rear seats (put 'em back when you need them) - mine are rarely in the car! - 20kg
Lose the spare & jack etc. - when was the last time you had a puncture?
can of mouse - 20kg
Junk out of boot, glove box, door pockets, footwells .......... 10kg
Assuming you have 60bhp and 800kg, you've just gained 5bhp
before - 75bhp/tonne
after - 80bhp/tonne
Dave
(nearly 'chipped Dci' - payday!)