What could I do to a give a plane an emergency boost of power for takeoff?
That really depends how safely you want to get off the ground.
If you are looking to get in and out of tight airfields using STC'ed parts you may want to consider a STOL kit which can modify the plane such that you can utilize a shorter runway.
There are some airframes that do have horsepower increase modifications available but that takes actual mechanic work and wont really be feasible in your &quot;pinch&quot; scenario.
There are a few aircraft that can be operated with JATO rockets and it looks like it was done at least once on an ercoupe during testing
You could add Nos but then again most pilots prefer their engine to run for the duration of the flight... You would also have to contend with the fact that adding NOS may very well require a direct port bore, which is no small job.
Afterburners don't really apply to internal combustion engines, at least not ones that generate meaningful thrust...