Invida isn't to bad. Every exhaust I have installed has it's own issues. The Invida exhaust is a 2.25 inch system, same as CNT fits tight under the car for a clean look. ARC / FI / Greddy / true 2.5 inch exhaust, some hang low and scrap after suspension mods. Rule is never go over 1/4 inch over stock in exhaust diameter, when you do your engine performance drops (unless your boosted of course). So get what you want, you don't need brand name to get the sound you want.
Buying exhaust is just like you said, getting the right combo of parts to get the tone your looking for. HP gains you wont even notice there so small. You get more HP gains buying light weight rims and tires. I had FI High Flow CATs and FI Carbon Fiber Cans. Loved the sound but couldn't here myself think on long drives. my car has 70,000 miles so i needed a quiet system but didn't want to loose low end torque.
1st - I swapped out HFC for ARC Test Pipes after hearing FootLoose's set up. It gave me a deeper growl.
2nd - Left test pipes on and researched the look and sound i wanted. I didn't want the Fart Can look some systems give our cars. I liked the resonated look and sound. I found 2 systems with that look and sound, ARC Grip and CNT. CNT uses cheaper material and cost 1/2 as ARC Grip. Both sound the same, quiet under normal acceleration but awesome when hammered.
My car is not boosted at the moment so 2.25 is good for me, I still auto cross and drive hard but I have better low end torque with the 2.25 tubing, stock motor. Not going over 55/65 on these courses, don't need 2.5 system (For me)
Buy what you want and get the sound you like. I am planning on building my own after my engine and turbo install. For the gains you get with 2.5 inch exhaust I spent my money on suspension parts that makes my car handle better & drive quicker.
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