WIth the MAF disconnected the engine is running off a guess and it isn't always right. This explains why it doesn't like to rev. That'* a very important sensor.
Maybe you're just not experienced with FI or something, but disconnecting sensors long term is not a good idea.
A new engine will not fix your problems, It will only complicate them.
Here'* how you should fix it:
Get a volt meter, adjust the TPS properly.
Get to a scantool and verify that the MAF works.
Get an exhaust backpressure guage. Verify that it is within normal limits.
Here'* some poor redneck tips:
If you have a welder, cut the exhaust off in front of the cat to see if it runs better. If it does replace the cat, If it doesn't weld the cat back on. If you can't get to a scantool, Buy a MAF and try it out. If it doesn't fix the car take it back. If it does keep it. Look at her car and put your TPS as close to where hers is as you can.