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1999 Tacoma Fuel Problems

I have a 1999 Toyota Tacoma 2wd with a 2.4 liter inline four and automatic transmission. Do to high milage(218,000+) I decided to rebuild the engine and have the fuel injectors sonicly cleaned. The truck has been up and running now for about three weeks with two problems. The first problem is the CEL is on with a code for catalyst efficiency below threshold. This code I am ok with and have ruled out all other components except the catalytic converter. This issue was present before the rebuild. I just haven’t had time to replace the cat. My main problem is with my fuel pressure. The problem arose as a hard to start issue. The engine would crank but would take longer than normal to start. I have tested all of the associated relays and switches, etc. and have found no faults. I inspected what I could of the fuel lines(pressure and return) and could find no breaks, kinks or internal restrictions. When I perform a fuel pressure test, the results are as follows:

Key on engine off =fuel pressure at 48psi

key on engine on and during starting = fuel pressure at 48psi

with the engine running when I remove the vacuum line from the fuel pressure regulator there is no change in fuel pressure.

After warming up the engine and turning everything off , the fuel pressure slowly leaks down to between 0 and 10 psi. (approximately from 48psi to 30 psi in 5-7 minutes, and down to about 22 psi in twenty minutes.

At this point I am not sure where to go next. Should I replace the fuel pressure regulator or are the injectors leaking, or a combination of both?