Fact or Faction - Rims and Exhaust

[JeffAU1]

Hey all

My last post was about being told wrong information from my local Ford Dealer... And now ive been given alot of information and i am just trying to find out how much fact or fiction there is.

So any info you can give would be great.

Firstly:
You can see my car by my signature below, and ive bought some 17" Rims. I want to get it lowered by 30mm. Someone (Im not quoting names to avoid issues) told me that if i do this it will scrape on everything, and i may have to take alot of driveways and speedhumps on an angle. The solution i was told is that i must have either 18"'s or 19"'s. Is this true ? Or will 17"'s be Ok ? how much truth is there in this ? used:

Secondly:
I was about to book in a exhaust upgrade for a full 2.5" Exhaust with High flow Cat and Extractors, but after listening to a V8 with exhaust it may be a little to loud. I was told there was a similar noise level between the two ? Is this really correct ? used:

So then i was thinking of going extractors, high flow cat, and keeping my current 2 1/4" exhuast, and was told this would still give me the same power gains / throttle response / and fuel economy im after... Is this really true or would I be wasting my money doing this ??? used:

Sorry to ramble on but i need these things cleared up b4 i go and spend my $$$$.

Cheers
Jeff