RB makes the best bolt on solution, but its pricey. The street port long primary is the best.
They are well made and last so picking up a used one is an option, I got mine for $400.00.
You can read the tech articles on their site to gain a better understanding.
http://www.racingbeat.com/mazda/perf...y-exhaust.html
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1980 GS stockport, Fat Nikki, RB Dual Facetfuel pumps, Holley regulator, RB Street port exhaust, 2GDFIS, MR2 MK I electric fans, 2G strut bar, relayed fans, lights and fuel pump, LEDs
Project Fat Nikki Budget 12A rebuild Video setup < $30.00