@mirfan
Use the platinum plugs or whatever your car calls for...Using 2 tip or 4 tip won't make much difference... Infact in some cases it will damage the engine...
If your car is poor on acceleration... get the tune up done..
Plugs, wires, fuel filter (on gasoline engines)
If that still doesn't help.. thats how your car is...
With the AC on.. most cars do slow down a bit...
It's like if you are running and I make you lift 100 pounds of sandbag with you while you are running... are you still going to be as fast as without the sandbag? I don't think so...
so my advice to you is.. get the tune up done.. with platinum plugs or whatever your calls for... and save some money for future repairs...