Because the same 12 bolts hold the intake AND exhaust in, when you take 'em off the whole thing falls apart. As far as the injectors, you won't if you're careful. I did my headers and just unbolted the big bolts, which are a PAIN to get to. I say, if you've got to replace it, get nice headers. I got a set of pacesetter headers for $225 shipped. got 'em on eBay.
"Nitrous? So is that like viagra for your Jeep?" -mom
"I flopped it"