will running 2 mufflers cause my car to lose backpressure therefore lose horsepower... or will it actually add horsepower??

actually it will make you INCREASE backpressure making you LOSE HP.

less backpressure = more exhaust gasses are still in your combustion chambers = less combustion = less power.

that is unless you have a custom header/exhaust manifold designed for dual exhaust, in which case you would reduce backpressure and increase HP.

some people say less backpressure will make you lose bottom-end torque but i've seen dynos that say no such thing.

bottom line: two mufflers may look good but most of the time it hurts performance.

by the way, i don't think your malibu can top 140mph so why did you pay for Z-rated tires?

o i see you have a wing. please disregard previous post.

the sarcasm on the wing isn't needed...lol but about the z rated tires... i had my rims and tires paid for a few days before i picked them up... the company i was buying them from sold one of the tires i bought and it was the only set they had.. so i can't roll with only 3 tires... so the gave me those tires at the cost of the ones i bought...