New trucks don't sound like old cars - why?

a lot of it is in the mufflers
see if this makes sense...same car, different exhaust

this one is with you're basic summit 2.5 kit




and this one is with an x pipe and pypes M80 mufflers





now, ill have to check my dates to know for sure, there may also be a slighty displacement discrepancy (you know, 360 to 408)