Fuel issues/ afermarket parts

I currently own a 02 Impala w/ 3.8, 27,000 mi. and i got 2 questions...
1. This car guzzles gas like its no ones business, and to me, it runs a little sluggish. Would using a high octane fuel help, and also, is there a certain brand of gas that seems to work better with is car?

2. Where can I buy aftermarket stuff for this car? Im wanting to get a aftermarket grille, and either a CAI kit, or something to turn it into a ram air setup..

I probably sound like a broken record in this forum but bad gas mileage and sluggish performance are classic symptoms of a CAT going bad... Although you only have 27K miles, so maybe it's kind of early for a bad CAT...

Are you what I call a "digital driver"??? Either wide open throttle or full brakes while you drive???

I probably sound like a broken record in this forum but bad gas mileage and sluggish performance are classic symptoms of a CAT going bad... Although you only have 27K miles, so maybe it's kind of early for a bad CAT...

Are you what I call a "digital driver"??? Either wide open throttle or full brakes while you drive???

Well, I do keep it around 75-80 MPH while on the freeway, and Im not a fan of brakes, so I try to keep off of them if possible. But I just filled my tank up with 93 oct. fuel, and installed a K&N air filter.. I hope this helps...