So, a little background. I have 3in downpipe, Rtek1.7, 820cc secondarys, boost gauge, aluminum radiator and thats all my mods. Ever since I converted to aluminum radiator, after I drive my car around town for about 40mins, the idle will start to wonder just a little, idles at 900, when issue starts, drops down to 750 and wonders a little. Once I start driving in this condition, it will start bucking and spitting, sometimes its really bad and sometimes its slight but still noticeable. I am stumped, anyone care to chime in?

 

Are you sure you don't have 720cc secondaries? That is what you should be using with a rtek 1.7. I am assuming primaries are stock?

 

When was the last time you changed the o2 sensor?