I Need Help I just buy a 3000 GT VR4

[3000 GT VR4]

Hi I just fond this Forum and I think is great.
The Car is in good shape only have 45K miles. But have something wrong in the RPM Tach and others thinks, I hope all of yours can help fix the car.

1) The tach at 3700 RPM and the the car go like the engine will explode and go at the speed of 75 miles Or 120 Km/h in 2 Gear.
How can I fix this ?
The speed is true because I read in my GPS the same speed.

2) the aero only works once and the the red light go on in the dash and don't work more until I shut down the car and then will work for only once again.

3) there are another think but I will like to fix the Number (1)

Any Help Will be apreciate.
Thanks.

[cotmfk]

Hey! Welcome to the club! Check out 3si.org and there will be a lot of help there!