The 6spd (94+) really gets the most out of the stock turbos, which drop to 11-12 psi past 5500 rpm no matter what. Shifting gets you back into real boost again, meaning acceleration is steady well past 100 mph.
The stock catback (3 inch till the mufflers) can support 115 mph traps before becoming a restriction so don't let it fool you. The real gain in power is a 3-inch downpipe and losing the pre-cats (actually, 2 small cats after the turbos but before the main cat). A car with a downpipe and boost controller can trap 105-107 mph and look stock doing it.
Though a neglected example will be slower, it doesn't take much to keep 'em going. New plugs & wires, an o-ring for the rear turbo-to-IC pipe connection, and maybe a fuel pump rewire and they're set.
My usual example for people wondering what they'll do is I put a MBC and K&N on a friend's 92 Stealth (150k miles) that he'd bought a week prior to the track day. It ran 13.2 @ 103 with nothing else done to it.
If my car hadn't gotten me arrested twice, I'd still have it