how fast you can go is a direct correllation to how much money you are willing to spend. My advice to you is to sell it and buy a car that's designed with performance in mind. Modifying a car like that is a receipe for frustration and lots of wated time and money. Hardly anyone makes performance parts for it either.
You could buy a late model Supra twin-turbo, a Miata, a VW Corrado, an older M3, a Corvette, RX-7 or many many other cars for less than what you could sell the Montecarlo for. They would also be a lot better investment considering your goal, and a hell of a lot more fun to drive. But what exactly do you want out of the car?
The basic performance mods go like this:
2hp, ุ, K&N filter and/or intake. I like to make my own cold-air intake with dryer hose.
4hp, 趚, cat-back exhaust system
5hp, 贄?, performance chip (if available)
8hp, 赨, headers
cam, underdrive pulleys, intake p&p, bump compression up, etc etc there's a lot you can do, but intake and exhaust are what you need first
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