after installing all new gages the right side works fine, the left side oil pressure gage pegs when u turn the key and the tach goes to about 300rpm when u turn the key off. only on the left side does this happen

I believe the gauge that pegs is going to ground and is either wired wrong or there is a short.

when i unplugged the sender wire it goes back to zero, do u think the sender could be bad?

Could be BUT unlikely that wire should be grounded out some place between the sender and the gauge.