I'm interested to know what is the best improvement you have made to your car. No matter how big or small. I got this seat gap pad filler that fits between the centre console and the seat. No more trying to retrieve your phone or parking tickets for 5 minutes being on all 4s with your butt sticking out of the passenger door and then emerging with multiple scratches on your hand. Such a simple thing but really effectively. I bought it on Aliexpress for a few pound. It doesn't look good when it's in your hand but when it's in position it blends in really well. Does the job really well.