Thinking this car is from hell,
It's a gen2

The list of problems never ending
Cars miss fireing changed leads spark plugs fixed for abit then miss fired again,
Alternator given up? Or have I forgotten to connect a plug? I did pull the Inlet plenum off,
Can I use a Camry or Celica alternator?
Vaccum leak is an absolute drainer I DNt know where it's from anymore sounds like its from inlet area
Trying to clean up the wireing in engine bay n keep finding new plugs that go to unknown locations,

I've spent more time on the car then with my miss's n my cars spent more time off road then on

I have never had issues like this if anyone can help me ill be u a slab:p dead set its such a pain in the *** to just watch the car collect dust

Try replacing the distributor cap. And also pull the plugs out, they may have fouled up again. If so then there's finding out why.

Hi,
Okay for your misfire, your changed all leads and spark plugs right, including the coil lead. You could also grab another coil, change distributor cap and the rotor button. Check that all your leads are in right first though, even doa  risistance check to make sure you don't have a dodgy lead out of the box. I just had to send bosch leads back as one was arking withing 500km's of driving.
For your vacume leak it could be comming from anywhere. Get it to a garage with a smoke machine. Basically they will smoke up the intake and you will be able to see any vacume leaks straight away.
If your doing an at home test your can spray water on the area and see where its sucking in water from but being an MR2 there are only a few areas you can test like this as most places are hard to get to.
Sometimes you need to cut your losses and get it to a god garage, not worth the stress.
 

Okay. Hace you pulled all the plugs out to compare the color. If one cylinder is missfiring hopefully the plug color is darker then the others. Ideally your spark plug colors should be brown, if you got a misfire from the same cylinder and its frequent enough that plug will be black.
I take it its only misfiring under load or higher rpm's? Plug color test is yoru best bet.
Low voltage from alernator will also cause misfires so maybe test that. Lastly check your coil is okay. You could possibly have a cracked coil casing.
Try the water spray test for your vacume leak, could be your intake manifld not seeling up properly. Try spraying your intake pipe and couplers. Where are you based out in the country side or something? Don't know what options you'll have for a good garage.

Obviously disconnected plugs are not good.
I would get an engine wiring diagram and start checking and ticking off the major sensors.
Then do a diagnostics test and see what codes you get.
Wiring is not hard just time consuming, and need to be methodical.
Vacuum leak, check all the hoses from air flow meter back to turbo, intercooler, intake, and all of the smaller ancillary hoses especially around the blow off valve and turbo.
Unfortunately, you have a car that has probably been fiddled with by countless owners and mechanics so you have to correct all those mistakes...

Have you done a Error Code test yet?

"Alternator given up? Or have I forgotten to connect a plug? I did pull the Inlet plenum off,
Can I use a Camry or Celica alternator?"


Things to be aware of when looking for alternators.
You would be best to look for one from the same year/model as your car.
MR2 turbo alternators have a larger mounting bracket, so an alternator from an NA model will not fit the turbo bracket, and they have different current outputs.
Also earlier model alternators have a round plug while the later models have an oval plug.
 
I'm not sure if one from a Camry would fit the turbo mounting bracket, or have the right plug or current output.

http://www.mr2oc.co.uk/know-your-2-knowledge-base/mr2-mk2.html?kbartid=162
diagnostic check... do this first.
(you are all over the place by the sounds of it)
manuals and wiring diagrams...
http://manual.teq.org/MR2_SW_1993_REPAIRMANUAL.zip
http://manual.teq.org/MR2_SW_1993_ELECTRICALWIRINGDIAGRAMS.zip

Have a look in the for sale forum, there is a few people wrecking MR2's and I'm sure they will charge less than $250, even with postage haha.

post a pic of these so called wires and where they are in the engine bay, someone here might help you as to where they belong
i had some stray wires and did exactly that and got the response i needed and they are all plugged back in properly now
one of those was the gearbox earth plug lol.
cheers