Won't go above 45 MPH

[Mike]

A buddy of mine recently purchased an '80 or '81 Trans Am that had been in storage for 9 or 10 years. The car has low miles and was owned by an older lady since new. The problem is that the car won't go above 45 MPH??? It has good take off but once it gets to 40 to 45 is bogs down. He's talked to two mechanics and they both said it needs a motor rebuild at a cost of $5K. He said the oils clean, it doesn't blow smoke and there's no apparent leaks anywhere. Are there any emissions controls that might be holding this car back?? Anybody else ever experience this before? I just find it hard to believe that it would need a motor rebuild from sitting for 9 years. I could see the valve seals needing to be replaced but that shouldn't cause the car to bog at 45.

Thanks for any suggestions.

Mike