I agree, build it the way you want and run whatever PAX you have to, way more fun that way even if not the top dog you can be happy with beating cars that are supposed to be faster, something I have done for decades after I got tired of winning all the time.
Wider wheels absolutely though in most cases pick tires based on real specs like tread width, section width, weight, etc but also ones noted for the best grip and feedback even if a bit narrower. I generally run 205s on 8's, 225's on 9's, etc but in autocrossing you can sometimes be faster on wider tires like a 225 on an 8.
Consider 4x100 conversion, my 15x8 6UL wheels are 11.4 lbs, single biggest overall improvement to any modded car is lighter weight wheels and tires as it improves every single aspect of performance and reduces wear on the suspension and chassis and will ride better, all things balanced out like spring rates, dampers, etc...
Sway bars, likely not needed, upgrade front bushings and get adjustable links to take out any preload.
Sleeved suspension bushings can really help the car react more directly since not winding up and down like rubber bushings do when flexing.
Take all the weight off you can, move some to the rear, keep it low and best between the axles and centered or offset to passenger side to better cross balance the car. Add weight only if absolutely needed.
Forget braces very likely only going to make the car slower by adding weight as the car is quite stiff already, spend the money on real performance, not placebo parts. The only brace I have is a two point on the front crossmember I made from scrap metal, two bolts and two rivnuts. I have built many autocross and track cars up to full race cars and studied every major suspension book published so have a pretty good clue of what I advise but of course there are always exceptions
My car is setup for street and track so a few things mentioned might need addressing a bit differently for the rapid fire weight shifts of autocrossing but I would not stray to far. Unfortunately many parts are made for profit with little or no real testing to improve anything but the bottom line of the company making the parts and those selling them. If a part added weight and made the car faster it would have it as long as it did not slow it down in one area or more just to be faster in another aspect, all about balance, in all things.
Rick
