I know that there's a ton of info about these mods on this forum and others, and I've been trying to wade through it all. I am trying to figure out what makes more sense for a $2-3k investment for my '07 Z4M Coupe, which will see primarily street duty with perhaps a track day here or there. Also don't have the time or tools to do my own work, so have to factor labor into the equation...
Seems like headers are usually recommended as the go-to performance upgrade, but my car needs to pass OBDII readiness emissions tests, and I would need to have customer work done to relocate sensors or buy euro cats, and likely also need a tune, not to mention that some still seem to have issues? I like the idea of headers, as it would enhance the sound of the car as well, but seems like this could get very pricey and complicated, no?
Or, I've seen several happy endorsements for swapping out the rear diff for 4.10 gears? I don't care about the slight reduction in top speed or reduced mpg. Seems like an excellent idea for the $$$ from all I've read, but not sure why almost no one's done this but everyone here seems to be running non-stock headers?
Any input welcome! Thanks
Edit: Also would like thoughts about tunes (ESS/Evolve/Etc) with stock headers as not many seem to have gone that route. Worthwhile? Running AFE intake and SS Powerloop mufflers, otherwise stock.