Engine Hesitation/backfire problem solved

I have been running a lot of injector cleaner through them lately. Mainly Lucas, with a dozen or so tankfuls of fuel. So, I am thinking they are not too dirty. Could the o-rings have broken or split? Maybe the pintle caps? My symptoms act like a lean mixture. I have gone over the engine several times and have not found a vacuum leak. I am wondering if an o-ring has split and is sucking air there.

I was having a persistent problem with hesitation, backfiring up through the intake, and general misfiring and running badly. Classic vacuum leak symptoms. I went over the vacuum lines many times and found nothing. The ECM was only showing code 94, but not 44. I went through the thermactor system a couple of times to verify it was correctly working. It was. The cylinder balance test showed nothing. Compression test showed all cylinders good or better-than-good. Fuel pressure was running 42 without vacuum and 34 with. Then I got to thinking the old, original injectors may be clogged or something. Maybe split o-rings or shattered pintle caps. So, I pulled them and ran carb cleaner through them. None were dirty and the spray patterns were all OK. I had been running tons of injector cleaner through the car for months prior, so I felt the injectors SHOULD be clean. The original o-rings were in surprisingly good condition, and few pintle caps showed any degradation. Put on new o-rings and pintle caps. Put it all together and it ran worst than before. Thinking I had got some of the injector connectors crossed, I pulled it all apart again and found no problems. Then, when I put it all back together again, it still ran badly, but read a 1 on the balance test. Swapping plugs and wires from 1 to 2 did not change anything. New cap and rotor changed nothing. Swapping injectors 1 & 2 moved the balance test results to 2. Installed a rebuilt injector this weekend and it runs like new again. AND, the persistent 94 code went away. Balance test returns a happy 9. I believe the injector was failing slowly, and only showed a problem under load, maybe this is why the balance test did not see it. The engine did idle nicely and started every time without an issue. So, I am thinking that the 94 code was kind of a red herring. There was no problem with the thermactor. The computer may have been seeing the lean mixture from cylinder 1 and could not tell what the problem was. But in the end, I still have 7 of the original injectors in there and functioning nicely.

I am thinking the injectors should be better quality than this. I mean, it is ONLY 30 years of daily driving with ONLY 270K miles. I'm thinking, WTF??? (sarcasm flag raised high here).
I'll put this car's quality, year for year, mile for mile, up against any other make or model, foreign or domestic.

Not only that, But Quality is JOB 1!!

I love how she runs now. If I can only get the cruise control working...