BS deletes are cheap too.
As for tuning, talk to Walter at marcy motorsport about a tune. You don't have to run 91/93 to make power on these cars. You can get just about the same from running an 87 tune, and save money on gas.
If you are wanting to get exhaust, get something 2.5in, and if you plan on running a header later, first when you get a tune, make sure they fix that so the header will go without issues, and second, put a cat in there cause it will be really loud even with both a resonator and a muffler.
When you clutch starts to go, put in a flywheel and clutch. Talk about removing rotational mass. If you want a little more power, put in stage I cams.
Even without the cams, you can make some decent power, just one little thing at a time.
2005 Focus Zx3 se D20 M5 - "Helios" - blazing copper
intake, header, exhaust, xcal2 tune, !CMC, cams, suspension, nitrous, torsen, spec lw flywheel and stg1 clutch
home brew turbo in the works