I've heard a lot about how losing backpressure in your exhaust kills your torque...like...eliminating all backpressure will really hurt torque...but help high end power or something like that?  Anyone have any info on this rumor?

All engines need a certain amount of backpressure for best performance. The exhaust needs enough velocity for proper scavenging of the cylinders so complete combustion can occur. It's a real science determining the proper amount of backpressure for any particular engine...the desired power level...the rpm's the engine is expected to run at, the displacement of the engine, etc. The factory specs are a real compromise that take into account emission regulations, cost effectiveness, performance, durability...in other words, a lot of different factors.

Look at a parts catalog and you see a variety of headers and their specs...each aimed at a specific performance level. Race only headers are designed for wide open throttle high rpm use...using them on the street will hurt low end torque.    Street headers are made for low and mid-range torque, and will suffer on the race track compared to race only headers.

In general, reducing back pressure is good, but it needs to be done in concert with other modifications to the drive train for the most efficient perfomance.

so...what about in use of hooker's super competition sidemount headers, with sidepipes?

I figure since I'm making a car that I want to use every now and then on the drag strip, I should have some low-end torque.

CorvetteRacer197038453.3688888889

Get a high stall converter and good flow heads and a higher duration cam to maximize the flow of your headers. low rpm power and torque will be hurt so thats what the high stall converter and 3.73 gears will make up for.

More important than backpressure is flow.  If the exhaust is too large ( too little backpressure ) the speed of the flow is too slow.  Smaller pipes/headers will speed up the flow. 

An object in motion tends to stay in motion.  Also true of exhaust gasses.  Rapidly moving gasses create vacuum pulses when the exhaust valve closes.  This create a vacuum on the next exhaust valve to open.  This helps to evacuate the cylinder.  The more exhaust out, the more fresh air/fuel in, and the better the performance.

Larger systems work well at high speed due to the increased flow in the  system.  Smaller systems work well for lower rpm.

There is a bit more to matching it up.  You must also consider the volume of the engine, and how well the engine breathes.  This depends on the intake, cam, and heads.  It's all matching to what you have, or what you are buiding.