Loyale7595

When i dont have the transmission in gear it will rev up no problem but when it's in gear it doesn't want to go and when I press in the gas pretty good it will down shift of it will even go???

How do I go about doing the vaccume test?

I'm not really sure it was a one owner it only has 100,000 miles in the last 10 years they had it they only out 2,000 miles on it then it sat for about 4 years I bout it from a dealership not running got it going on about 2 hours changed the fuel fuel filter plugs wires oil alternator and since I got it to run it still won't go over 55mph and not sure what I can or need to do to get it to go faster

What engines will fit on these loyales or what can I do to it to gain power it won't go over 55mph