[IanH]

change the inner injectors to the outer positons to help diagnose the problem

 

[IanH]

so can you put a meter on the harness and check the signal while its running, assuming its not the injectors then its the harness or ECU.
Are you sure its not the spark ??

 

[IanH]

first download the FSM at phatg20.net
if the timing is messe dup the ignition timing will also be messed up.

 

[IanH]

you will have to rotate the crank up to two revolutions before the marks line up.
As Was says its unlikely that its skipped a tooth, download the FSM and take a look.

 

[IanH]

then do a compression check on all 4 cylinders
this will tell you for sure, did he do a proper leak down check ? I don't understand what he did
Reading should be 165 -195 from memory

 

[IanH]

Then most likely is a blown head gasket and head may be damaged / warped.
Timje to decide on either a repair or a low mileage replacement.If you are doing the work you could lift off the head and see how bad it is. before spending any money.
Someone quoted $300 for a re-built head, i think you could get an engine for not much more than that.

 

[IanH]

sorry about typo