If you are not driving your car for offroad use, where extra power and less weight matters THE MOST, I wouldn't advise doing anything of that sort is not really a good idea. Even for offroad max weight reduction you can go third row seats removal, but not the spare tire removal. One of the most important safety aspect for any car is its spare wheel, no matter how less u used but that one day need justify all the extra weight.
For gaining extra power you can look into small and economical engine mods like: switch to Iridium spark plugs, K&N free flow air filter and throttle body spacer. If you want more power, then change to free flow exhaust system (cat back) and then change the headers (but this will make car very noisy). After all this you can go for chip tunning which will fetch you atleast 10% - 20% extra horsepower.