Polini is a straight slap on, just chamfer the ports, upjet that 14.12 sha and bam 40mph stock sleeper. This kit needed a decent amount of clean up on the flanges, and the ports had some boogers inside them, 30 minutes with a file and it was ready to go. Next the piston is a lot harder to get in on this kit, I recommend slipping the piston in the kit first then putting the wrist pin and clips. Also it took about 3mm of base spacing to get the piston to clear the head on the cases I used. As far as performance it has slightly more torque, you might expect this with 1mm bigger piston. the intake flange has more meat for enlarging, enough to go to say 23-24mm, exhaust is about the same. Only draw back that I can see with this kit is finding the right sized piston! Get these while you can, if you are willing to put it a little more time and get more bang for your buck this is the kit for you!