Just in case you don't get the PM...
Hello, Sorry for not getting back to you as soon as possible.
Okay there are a few tweak's that are easily DIY for tuning the 1.6 engine. Most are pretty cheap as you can steal parts from the older car engines or adapting items. However as with any tuning you can throw money away on loads of expensive shiny parts which is the best route but also the most expensive.
We will start with where the air comes in
Air filter > Options are a panel filter (Best bang for buck) Something like a K&N panel filter, Next up is a BMC CDA. This is expensive but made from carbon. Both help breathing and torque. £30-£200 +5hp and Torque
Throttle Body > Can swap to the 1.8 or 2.0 Direct fitment and has a larger circumference of about 23% last I checked. Will probably hinder a little power low end but as the 1.6 has the same bore and valves as a 2.0 you can get it breathing higher the top end of the revs. £20 +2hp top end of the rev range
Intake Manifold > Change to the 1.8 or 2.0 manifold. Will require a new brake servo pipe as its positioned. The 1.8 and 2.0 has a varible intake manifold. This improves torque mid range by reducing the length of the intake from the throttle to improve torque. Will need an ECU adjustment to turn it on though.
Camshaft > Replace 1.6 with a 1.8 or 2.0. Slightly more aggressive than the 1.6 and lobes have longer duration. Will mean doing a cam belt to remove it but a pair can be picked up for £50. 5+hp
Exhaust > Remove Pre Catalytic convertors to a CF2 engine downpipe. Will need to weld in new Lambda bosses and requires a new flexi joint to the third cat. Autolusso supply a kit for about £150. +5hp +Torque low down
Exhaust > Cat Back system. Improves breathing and sound +1 to 5 hp + Torque £150 to £300
Crank Pulley > Under drive and lightweight crank pulley. Free's up Inertia in the crank. Also the Aux belt moves 30% slower than OE meaning alternator and power steering are not powered as highly. +10hp £50-70 Also improves throttle response
ECU > Remap improves all the above modifications by adjusting the ignition map and fueling to respond to the tuned parts. This will be worth about 10% of the power so 10-15hp. Same in torque. Also you can turn on the VIM option further improving
Those are the easier cheaper things you can do on the cheap.
You could Lighten the Flywheel. This will again reduce inertia and mean the engines spins up and slows down quicker. Improves response and free's up a bit of horsepower (Think of a motorbike engine and how fast they respond to the throttle).
But all the cheaper things above to the engine will see a 1.6 hitting 150-160hp.
But the issue with all that is for about £200 and a weekend's work you could put in a 2.0 engine and it would have that power in standard form without trying... Which is why people then to choose the biggest engine they can.
Alfa 166 2.0 Twinnie - LPG and a few trick performance parts