There are a lot of these products out there that are crap. Most of the ones that recommend you use them often are really ineffective and pointless. There are some serious FI system cleaners that do the job, and you only use them once or maybe twice a year.

For routine cleaning, I use Techron. Put a bottle in the tank, and do the 'Italian Tuneup' (run a few miles at high RPM, like 4500, to really heat up the engine, cool down, repeat a few times). This gets carbon deposits loose and out of the combustion chamber. Be sure to change your oil after running the Techron tank through - leak-through chemicals can break down your oil.

For heavy duty injector cleaning, BG44K is the best solution I know of. This is serious stuff, and there are probably some other BB members who know more about it than I do.

Another thing to consider is the quality of gas you're using. Some brands contain additives that just don't sit well with our injectors.

And finally, if you don't often wind out your motor, I recommend that you do so. At least once a week, when the car is warmed up, run it right up to the redline once or twice, someplace like a highway on ramp, or the road out of town. It does wonders for preventing deposits from forming on injectors and valves.
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Speed Racer, '83 240 R, '74 164 E, '93 940 OL1 (Manchester, CT)