Greetings. Please bare with my "simple questions" here. I am a newbie to my M purchased last month and its been 20 years since I tinkered with cars. I have access to a never used set of factory headers at a price of about $1,000. My 88 has original exhaust system. Questions: Anyone with experience removing stock exhaust manifold on these older engines and and install in such a tight space? Likelihood of busting a bolt? (hate to turn this into a major pain of a job). Also, with only enhancement to stock engine being a JC chip, should I expect much gain in hp and or torque? (10% +???) or ultimately just a nice improvement in sound as I would like car a bit louder. For the "hassle" and cost of system, better to let me and just upgrade / change exhaust when it goes? Thanks.

The best factory headers would be the Euro M88/S38 version. Even then, the US version isn't horrible. You could see perhaps 10rwhp if you switch to Euro headers. They look very different from US manifolds. The bolts get rusty, so snapping a bolt is a very likely possibility.

If you are dying for more power, and you are sure the car is in excellent mechanical condition, there are a couple of mods you can do.
1. Miller MAF setup -eliminate the restrictive AFM, will negate JimC chip, however.
2. 3.8L cam gear- adds low-end torque
3. Euro headers

...and that's about it unless you want to get crazy on it.