you seem like you are very unpleased with your purchase or at least thats the impression am getting. is pretty normal i guess for the E70 to feel bigger and maybe not as nimble as the E53 since in size the E53 is more equivalent to the X3.

performance...well yes the E53 is a little quicker of the line but not by much and when you say Slow? Hmmm, I dunno know, I still haven't come across a 4.6 or 4.8is that can out run me or outperform me.

For the exhaust, yes it weights almost 100lbs , i personally have the muffler delete and i love it! loud when it needs to be and quite enough for the family.

good luck hope you enjoy your new X

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"This is My X5 there are many like it but this one is mine"