You can use something really small in diameter to reduce the air flow. Try using single strand wire like stripped phone wire. Tie and superglue it at the top and wrap it downward. Then, should it present an error code, you simply clear the code and unwrap one round at a time until you no longer get error codes.
Just run a thin coat of glue down one side so it may be removed without difficulty.
Try that. I bet you'll (eventually) find the max level of reduction.
I removed the tie wraps as you said a few days ago, and cleared the “system too lean bank 1” error code. It has not returned. I did another thorough vacuum leak check, with Carb cleaner, (I am not set up to use propane). I found no leaks. I think the restriction I had put on the MAF tube, was just too much, and was the only cause of the error. I believe it is running to strong and smooth, to have a leak. MPG is improving some. See MPG update in groovy vehicle category.