believe it or not i turned quicker times in my 2002 gt with the factory spoiler off
Believe it.
There is a reason that some of the GrandAm and SCCA cars REMOVE or DELETE the "spoiler". Most folks don't understand that in the world of vehicle engineering and aerodynamics, a "wing" and a "spoiler" perform totally different functions.
LECTURE TIME KIDS....
Get out your #2 pencils.
In race applications "wings" are utilized. They are ugly as he** but, they are designed to create a direct and deliberate effect on handling and downforce. They are usually manufactured to be fully adjustable to suit the needs of the vehicle and track configuration. It takes a well-tuned and educated person to calculate the exact set-up of an adjustable wing.
"Spoilers" are used on most cars for looks or function. Those that are functional are installed to disrupt the airflow going over the car to reduce any "lift" that is inhenet in the body design. (Just look at an Evo, STI, my TA). In essence a spoiler increases the turbulence flowing over body design. This increases tire contact with the road, which increases traction which assists with turning, braking and accelateration.
The design of an immobile fixed design spoiler can either increase or hinder performance based on design and mounting. Most fixed spoilers on modern sports cars are designed to assist with low to moderate speed lift issues. Yeah, that it does but there is nothing more butt-clenching then an improperly designed rear spoiler at high speeds.
In the end it really depends on what you will be using your car for and for what percent of time.