Midlength question
 

Anybody out there personally Swith from MACs to A good set of LTs, oh say KOOKS? I am wondering as to what kind of gains to expect, I will say on a Naturally asperated car that, well, it breaths deep :devil: and yes... I am headed for the best almighty dyno number. (personal number)

You should feel a noticeable gain. Mid-lengths don't do much on our LS1's.

Totally not true.
My MACs with stock Z28 cats welded in the MAC Y-pipe (DO NOT use MAC cats) made 18-20rwhp out of the box. I didn't get to dyno them after cleaning up the flashing, nor doing the "collector mod", but I would project a solid 22-24rwhp.
I went to coated Hooker LTs as I was going heads/cam/nitrous and wanted the extra scavenging as well as the low-end torque. That is where LTs shine over mids...down low. Peak power is comparable, but not torque. Now that you have cheap LTs like Pacesetter, MACs have fallen by the wayside...
I don't have any direct dyno comparisons as the heads/cam were done at the same time as the LTs...
If you can find a set of inexpensive new/used MACs, they are a good-fitting, easily installed header that makes decent power. I sold my set-up for dirt-cheap...

For a max-effort N/A engine, the $1200 LTs will probably pick up 8rwhp. The cheaper LT probably more like 3-4rwhp. This is provided that the MACs have been cleaned up and had the ball-flange replaced...

yep its a complete MAC set up minus cats :) used the wire machine to weld in small segments of "special street legal cat tubing" :jest:

If you are going all out for a certain number or 1/4 mi time, then by all means ditch the MACs. They would make somebody with a lowered, bolt-on car VERY happy...