When buying my car the tires on the car were all bumpy rough, I put on new Lace rims and tires and the front tires are still fine. (No weight to wear) but the back are wearing uneven, the inside of tire is probably 10% less than rest of the tire. So its riding toed in. This is most likely alignment?

Maybe...
bad CA and/or Cradle bushings is another.
Alignment machine can be within spec and still have bad bushings.

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could this possibly be too much negative camber? more wear on the inside would be an indication of this.
Is it even possible to adjust camber, and how do you do it?

The old tires worn completely uneven bumpy all over. These are onlynwearing inside

So the old ones were like cupping? Check your shocks/balanced right... Inside would be neg camber, or if you rub your hand inside out on the tire is it smooth? If you do it opposite and it's rough, then that's called feathering which would be toe out.

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yup - there are a few things which can cause the "cupping"
ball joints. tie rods. shocks/struts. basicly - it is a symptom of a "loose wheel".
the wear on the inside would imply one of two conditions: toed out or too much camber.
and, the fun part is....any camber adjustment also changes the toe....
the rear alignment for Fieros is VERY fussy. bad rear alignment can make the car damn near impossible to drive in the rain or snow.

quote Originally posted by Pyrthian: yup - there are a few things which can cause the "cupping" ball joints. tie rods. shocks/struts. basicly - it is a symptom of a "loose wheel". the wear on the inside would imply one of two conditions: toed out or too much camber. and, the fun part is....any camber adjustment also changes the toe.... the rear alignment for Fieros is VERY fussy. bad rear alignment can make the car damn near impossible to drive in the rain or snow.

My fiero likes to spin in the wet, Look like a drifter every time i pull out or throttle.