That has nothing to do with your water heater and everything to do with your lack of a pressure tank to service a car wash for people. No home system will be adequate to run all of that at the same time. One at at time, yes. You would need to upgrade to a commercial level water delivery system, with added pressure tanks, to run the output. Then you would also need the 3" drain or 2 2" drains to deal with the output.

You run all those fixtures at the same time?

Or are you getting low pressure even when running just one or two?

Do you have just one supply line feeding all those fixtures?

Do the fixtures have volume controls or just on/off ?

We have 2 fixtures in each shower and they each have their own water supply with individual volume controls, but if you run both at the same time, you do notice a very minor decrease in pressure to each fixture.

You have unrealistic expectations.

How many of those heads / sprays are you running at the same time?