lol, I don't think I can write all this with chinese because I'm really bad at it, so here, lol
AEM v2s are alittle bit better than the most, but really the most you are gonna get is 5hp tops, its just an intake, but it is good for your engine, plus it sometimes sounds good, lol. Its usally like $300, so you could do is just order one off ebay, spray it with high slow heat resistant paint and buy a filter, KnR i think, its the same one AEM uses anyways, its $75 at canadian tire, the ebay pipes is about $10-30 tops, saves u money and it does the same thing.
I don't know what the thing is, are you talking about a cat-back system? It can get you around 15-30hp depending on how good it is. Its a must have, lol, because it sounds great, lol. Actually it does do good for your car, less resistance when the gasa exit from te headers, better flow = better power.
Check with the local performance shop and see if they carry the ECU and see if its street legal. Ask around lots of shops cause some of them might just want to get your money. If it is install it, if not don't cause the cop has the right to rip it out of your car if it's illegal and fine you, plus they are idiots so they miht damage something else.