Recreational Vehicle Lpg Tank Valve/gauge problems of the 2003 Chevrolet Cavalier

Speedometer sticking at 80 to 160 mph, even though the car has never ever been driven at those speeds, speedometer registars anwhere from 10mph to over the limit of the speedometer (180mph) when the car is shut off or stopped. This started at 25,000 miles on the odometer. The temperature gauge started registering over the red (and has actually touched the speedometer gauge needle) approximately 1 year later started at 32,000 miles. At 39,000 the gas gauge started doing the same thing. I have been driving with a portable garmin nuvi gps since 2008, just to use the estimated speed in the hopes I will not get a speeding ticket. The first time I looked down and saw my speedometer at 85 mph, I instinctively slammed on the brakes, and was extremely lucky no one was behind me. I was only going 50 mph at the time this happened. I now have a teen driver, and I cannot allow her to drive this car because she is not experienced enough to estimate her speeds. I will never know if my car trulely overheats because it overheats on the gauge 3-5 times a week. I have to fill my gas based on when I filled it last & how many miles I have driven since as I have no idea how much gas I have. This can be a very dangerous situation, that can lead to death and injury, as a told you my experience with instinctively slamming on the brakes, and I would hate to see what happens if I run out of gas unknowingly in the 3rd lane of an expressway. I also own a 2002 chevy Cavalier whose gas gauge registars 1/4 of a tank when it is empty. I spend over $450 at a garage to find out that the car was not breaking down, but was actually running out of gas. The 2003 chevy Cavalier of course has the more dangerous problem with the entire instrument cluster a mess. Unfortunately, the vecicle was not still under warranty with the low mileage, as it had been over 3 years. When are you going to do something about these cars? lets hope I'm not driving in front of your mother or daughter tomorrow.