A friend of mine told me 2 think about go for str8 pipes and forget buying an exhaust and something about removing resonators.

 

That will absolutely give you the best sound, especially from the V-8. It will also attract the most attention, especially from law enforcement. It will also encourage you to bury your right foot every chance you get. I had it for a while with my E39 and enjoyed it until I realized that I was really headed for trouble and had it changed.

 

I think that just removing the resonators you will have a future problem with the OEM exhaust (end section) since you will run "more open" flow . The OEM exhaust has a setup to work with the resonators.

 

Removing the resonators will have minimum affect on sound. Been there, tried that.

 

Based on my limited knowledge with exhaust modifications in relation to BMWs and V8s (though I did work at an import mod shop in my teen years that saw its fair share of Supras, RX-7s, and NSXs) I would assume that the removal of the exhaust and installation of a straight pipe from the header back would increase top-end horsepower at the costly expense of back-pressure (i.e. low-end torque.)
In general this = good for Autobahn-ing, not so much for stoplight respect checks.