EFC 38 is mild a stripper,md 80 is a real strong stripper. They both require an oxalic acid wash to complete the process. If you dont put on an acid wash you wont see the results of your work.
Not sure what you mean by taking the tint out I am thinking this decking was never finished.

I never use a power washer on a deck. If in fact you never put a finish on the Garapa there is no need to use md 80.

After the EFC 38 has been on for a few min say 15 min or so its time to scrub it off then rinse it off real well then put on the acid wash and rinse it off real well. Dry time put on the finish. J.

Thanks John for your response. I have enjoyed your posts over the past 2 years.

I can put the citralic acid on the boards, but will I just be brightening the gray wood? The gray didn't seem to come up with just the EFC.

The "tinted" boards were stained last year, but are mostly in the shade and still look pretty good. The problem is that they are only half of the porch, and the other half is the grayed new untouched garapa that is in the full sun. I wanted to stain both with woodrich wiping stain and have them look the same. Will the HD-80 strip the tint off the boards, so that they will not look darker than the new boards?

Gil,,,,its a two part system the brightner wont work with out the stripper and the reverse is true.

There is no reason to use HD 80 that is for taking off behr or thmposons or ato or some of the other junk on the market ghesssssss.

Just use the efc and the brightner, do some scrubing with a deck brush or some hand work and let it dry/ put on the finish. All the decking is not going to look the same right away. Finish the thing and leave it alone for a while. J