Way back when, when dinosaurs roamed the earth, there was a campaign for 86-87 3.8's.....
Quite involved and luckily, replacement parts were covered then under the campaign.....such as MAF, coils, etc.
You have the infamous Magnavox coil, which was prone to failure.....can do two things...check the output of each terminal with a spark tester(best thing to do), or ohm out each pair of secondary terminals(which may or may not show a problem).....I believe secondary resistance for these was 10K-12K ohms....if one or more pairs is out of spec, need coil....however, can be in spec and still fail, that's why the spark tester is your best bet......
Wires can't be checked just by looking at them.....not that expensive....
I doubt it's injectors, because it would do it every time.....
As for exhaust, an exhaust leak near the O2 sensor(like the seal at the ex manifold/exhaust pipe), could skew the data from the sensor(causing the car to run rich thinking it's a lean condition) and could even foul the O2 sensor....was vehicle scanned for codes? Don't need a code reader, can read flashes of CE light by jumping "A" to "B" in the ALDL connector, key on, engine NOT running......will flash "12" 3X's, and then flash any other codes 3X's in succession....when it flashes "12" again, all the codes have been read....bad O2 sensor could set a 13, 44, or 45 code.....however, those codes could also be set by other things such as a vac leak, leaking injector, dirty air filter, etc.
Could have a back pressure problem.....can test that by removing the O2 sensor, and attaching a pressure tester(need special fitting)....or you can create a leak at the exhaust manifold by loosening the bolts and creating a space(could create problems though, on this year car, if nut/stud threads are rusted bad) or by removing the O2 sensor and just briefly driving the vehicle....if you now have power where before there was none, then you could have a bad cat(most likely) or a blockage in another part of the exhaust(rare).....