Ok so I work parts, got a 87 gxl 13b, I see two type size injectors...6/87 and a 5/87...I'm guessing that's the year or build date? Alittle quick help to determine what I need for secondary injectors?

 

they are all the same size..primary and secondary and you do not need more fuel,period,with an N/A.
THIS Info is right out of the FAQ's(Frequently asked questions) thread that you should actually read.Just because it is Informative.
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Do I need to upgrade my fuel injectors in my NA?
Most likely, no. The stock NA fuel system can support up to about 250HP, which you will not be anywhere near unless you are running a big bridge port or a peripheral port. The stock NA actually runs quite rich, so you will see some gains by leaning out the mixture quite a bit. Adding larger injectors is just going to cost you power and waste gas.


What size injectors does my RX-7 use? What colour are they?
Year Engine Plug Size Colour Part #

84-85 13B NA, low square center, 680cc, orange, 195500-0900
86-87 13B NA, low square center, 460cc, red, 195500-1350
86-87 13B Turbo, low square center, 550cc, tan, 195500-1370
88 13B NA, high square offset, 460cc, purple, 195500-1350
88 13B Turbo, high square offset, 550cc, purple, 195500-1370
89-91 13B NA, high oval center, 460cc, red, 195500-2010
89-91 13B Turbo, high oval center, 550cc, purple, 195500-2020

 

pre 6/87 production injectors were low impedance (3 ohm), the rest are high (13 ohm).