1990 3.8 V6 fuel injection issue

Hello Tbird owners.. Just joined. Have a 1990 Tbird LX with 3.8 V6. I'm having an issue recently with I think... the fuel injection. After having put in some STP injector cleaner in the tank, a week later I'm starting to experience a shutter in the engine when going from idle up to drive speed.

At idle the engine is smooth as it used to be, but when stepping on the gas the whole car shutters with an unbalanced engine feel. I'm thinking I have a partially clogged injector in one of the cylinders but not sure which one at this point. As I mentioned, at idle the engine runs smooth, accelerate and it's rough or shutters. The only other possibility is a cam lobe has worn off and that cyl isn't producing power. But I would think even at idle, I'd feel a thump, thump feel as that cyl was operating. If its a cam lobe, the engine will obviously need a tear down and replace but it's an injector, any ideas on how to test and/or clean it out while still on the engine? Otherwise, removing the intake system may not be too bad a job to manually remove the injectors for cleaning. I'm sure hoping it's injection and not a cam lobe. I've always change the oil and filter religiously at 2000-2500miles so can't hardly believe a lobe would have smoothed off somehow, the engine has always experienced clean oil. Thanks for any ideas and suggestions.
 

biddle

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Added model year to subject.
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