Woah. That's alotta french talk in here. Don't understand what you guys are saying.
But in English, I can say, I'm with the guys with the bosch plugs. Even the Germans don't use them anymore! NGK. nuff said.
17* should net more than 160whp, but make sure the VVL kicks for both sides. Test each solenoid by itself and listen for the change in engine note.
The cat could be good, but keep in mind after 10 years the thing could be clogging up on the top end. Run open header on some runs and see the gains. You port matched the header too right?
For comparison, My VE made 169whp with 19* base timing, stock exhaust, and a JWT pop charger filter. Same SSAC header, port matched of course. SR16VE cams are usually good for 10whp or so iirc. I really feel like the exhaust is choking it....
Not to mention you have an SEL, and you automatically get a whp deduction for that