biturbo = better top speed, bolts right on, poor quality and will fall apart
technigas = does not bolt up and will require either a bracket to be made or purchased, sits lower, quieter and pulls better but has a slightly lower top speed.
Bullet = similar to biturbo, again does not bolt up correctly but works well and does not fall apart as fast.
Unipod filter works good, Puch 50cc high comp head works great, bolts right on and makes a big difference. 17.5mm PHVA works fine and bolts right on. There are no bolt on intakes for the stock cylinder so you are on your own. Motomatic pipe will not work very well with the stock cylinder because the timings on the ports are far too low. Porting the stock cylinder results in better performance than bolting on the Airsal 70cc kit, which I personally find to be disappointing. They vibrate a lot and do not perform as well as I would like.
22t rear sprocket, uni filter and jets, and biturbo get you to 42 or so, high comp head gets you there faster. Porting gets you way better results and makes the bike pretty fun to ride. Avoid the airsal kit.