well guys, everyone tells me that after they've done longtubes and cat-backs, its like driving a whole new car.

I did longtubes and true duals, and i could definately notice more power on the highway, but not so much in town. How much torque am i losing due to the duals?

 

probably none, it just seems like it to you, but if you put it on a dyno im sure its probably a lot better

 

You are losing some low end torque with longtubes, but that translates into higher rpm torque peak.

 

i was wondering, because my friends just feels like it pulls a lot more down low, but i can definately tell a difference from before and after, and it pulls a lot better on the topend

 

You probably aren't losing any; you just have a smoother curve.

 

that could be, right now i have a miss at 2500 that im still trying to track down, hopefully getting that fixed will help out a lot more too

 

This isn't true, headers will not smooth out a curve. Fuel and Ignition tuning will smooth out the torque curve.

Headers may smooth out a small area due to the rich stock WOT table, but not the whole curve.

When there is a change in exhaust/intake lengths (i.e. headers) you are moving around the torque peak, after it has been properly tuned.

 

Not enough back-pressure!

 

thats what my friends telling me too.
Im getting a tune hopefully soon, because id hate to drive a car to prom that backfires lol

 

Difference being, your friend is serious, and I'm joking! "Not enough backpressure" is the biggest myth ever! Trust me, dyno the car and see what happens ... the torque won't be less, just that the power increases so much more, it makes it "seem" less torquey.

... this is like the "LT1's make more torque than LS1's" argument .

 

I know i need a tune, because that backfire/miss has been there since i did headers/exhaust, and i had one code for left bank o2 too lean, looked at the o2, and it was wiggling itself out, so i tightened it up, havent gotten the code sense, still get the backfire/miss at 2500, its not always there either, which makes me wonder if its something with emissions being gone, but not tuned out. I think i left the air pump plugged in too. Air pump is bottom on the driverside, correct?

 

Yes, and longer tubes don't give more top end. Shorter tubes do. Thats why top fuel cars run short pipes for headers.

I've seen a lot of dyno pulls. Cars with headers are not more peaky. They usually have a broader (ie smoother) torque band.

Ream,
Velocity creates torque, not back pressure.