Cadillac Repair: 1989 Caddie tune-up, vacuum line, answer check


Question
What I mean about no power...is no power.  Yes it will rev up high.  At idle it idles, when revved up (while in park) it revs up high.  When placed in gear it has NO POWER to go above about 5-10 miles per hour.  
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The text above is a follow-up to ...

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Tried everything you gave me.  Yes to all questions.  No, if it is drive nothing happens (does not turn over). In my original messsage I failed to tell you I drove it around the block.....no power...it moves just no power.
 
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The text above is a follow-up to ...

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The engine was running fine....until I:
Changed the spark plugs...I used Bosch, cap and rotor.  That's it.
After starting it idles fine.  When placed into gear there is no power, forward or reverse.
Prior to changing the above it ran fine as was getting 22-26 MPG (highway).....after it the gauges was saying between 1 & 2 mpg!
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First, while the car is running, apply the parking brake and while your foot is on the brakes shift the car into drive. Can you feel the transmission shift into gear at all, and can you rev the motor while its in drive with the brakes applied? and then in park or neutral? Then shut the engine off in park or neutral, while the engine is off put the transmission into drive, and attempt to start the engine but DO NOT START THE ENGINE, if it doesnt turn over thats good. If it turns over you have a switch fault in the transmission.
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Check the throttle cable, and describe what you mean by no power, can you not rev it up, or only when its in gear it doesnt rev???

Answer
Take the distributor cap off and check the rotor with the engine off. And check the vacuum line going to the transmission from the throttle body, its on the transmission case not far from where the air box is. Next with the hood open and you foot on the brake, shift the car into drive, look at the motor while it shifts and see if the motor moves up and down, then give it some gas with your foot on the brake and see if it moves.
My next question is do you hear any popping from the muffler when the car is in idle, or any non-normal sound.