Originally Posted by Alex.Devol
Yeah it's to help benefit an upcoming remap, in about a month the car will be remapped after all changes are made, air filter & exhaust etc. On that subject I'm considering adding limited slip diff to help with traction, it's the only mod I'm planning that might come afterwards and Im still not sure if it matters whether or not that's done before or after the remap.. From reading up a bit more it seems like there actually are some really nice sounding diesel BMW, hotcoupe's for example.. But all seem to be 335s.. Since they are both 6pot 3 litre engines would the same sort of sound be achievable with my 325?
Alex,I can only echo what Jeff (acerboo) said about exhausts,and the potential to waste money.
To achieve your goal,and
increase the performance of your car,I'd forget any aftermarket back boxes etc,and go for a straight through custom exhaust system.
Find a good exhaust fabricator and have the pipework,backboxes replaced with a straight thro pipe from the DPF straight through to the rear,you could go for a straightforward single pipe with single/ dual tips,or if you prefer a twinpipe system (the single pipe from the DPF would split half way down the car) with either single tips,or doubles,any of the above won't make a difference on the power side,but could impact aurally.
The benefits of the above are,quicker spool up time on the turbo/s which reduces lag,an engine that revs better (due to the non restrictions of the now missing backbox/s)and arguably better MPG and more power.
A good custom straight through system is good for approx 10/15bhp.
An LSD is certainly an excellent mod (should be a standard feature,or at least an option on a RWD car,especially a BMW),one I would 100% recommend if you can afford it.
I don't think it matters whether it's fitted pre or post map, but you'd enjoy your car better if it was fitted tomorrow!