I just been reading thru this tread yesterday, i'm doing a semi 1.1 n/a tune atm u can check my thread out, dronners linked it in the first reply.
You can reach a decent amount im aiming around 70-75 bhp. Cost me 280 euro
till now, but then again i do everything my self, only thing i didnt do myself is head skimming.
I have a dremmel and do all the porting and matchporting with it, my mods are the following:
-Engine rebuild kit
-head skimmed almost max for compression increase.
-p75 866 cam, can be found in later p60 engines or 1.2 mpi 8 v engines
-p75 4-2-1 exhaust manifold (needs to be cut cuase its made for eninge with longer stroke)
-p75 throttlebody (needs to be matchported for 1.1 spi top unit)
-Match ported intake manifold
-Head port and polish (a small guide in my topic, with a link how the pro's do it)
-Other chip or ecu remap
- 1 3/4 inch exhaust no kat
- supersprint backbox
-cold air induction system.
Havent done all the above yet missing
the red lines, but will reach i guess 350-400 euro. Thats without lowering and brakes ect. Alot of work, dont think ull be done in 1 day. Shims need to be messured ect.
Tbh we can only give u advise, what u do at the end is up to you, be aware that here in holland tuning doesnt cost u insurance money, so i can drop a v8 in it and i still pay the same price wich is bout 30 euro a month,
Still planning to want some power out of ur car, do a engine swap, saves u loads of trouble and frustration, there is nothing worse then aiming for a possible bhp, and at the end not reaching it.
a p60 engine cost u almost nothign maybe 100 or so, easy to do urself cuase of the guides we got on here. The other 400 u can make ur car nice in handling, brakes ect. And ur insurance wont go up too much and u'll still have a blast in ur fiat.
If u want some advise u can always ask us.