Aem wideband
 

Is there any point for me to get this for my 1989 n/a rx7 or is it jus pointless to have for a non turbo car?

A wideband is a useful tool to have when tuning. The need for it will depend of the level of build you have. There are plenty of choices out there to pick from. Here are a few.

PLX: http://www.plxdevices.com/wideband.html
NGK: http://www.ngksparkplugs.com/product...rmance/afx.asp
Innovative: http://www.innovatemotorsports.com/
Zeitronix: http://www.zeitronix.com/
FAST: http://www.rpmoutlet.com/mt.htm
Autometer: http://www.aemelectronics.com/wideba...fuel-gauge-25/
AEM: http://www.aemelectronics.com/wideba...fuel-gauge-25/

Do you think i could get any significant performance boost from that on my car? All i have is aftermarket non restrictive mufflers and an intake though lol, the only other performance upgrade ive considerd is lightweight pulleys, but its 380$ and only claim 10hp increase lol http://www.srmotorsports.com/sr86plly.html .. But it says less belt slipping and whatnot so maybe it does make a little difference but other then that and if the wideband, theres not much other engine upgrading i can do without swapping/porting/NOSing my car :(

Anything well tuned will benefit from its optimal condition.Doesn't necessarily have to be built.

Widebands are for monitoring your AFR's, lean to rich conditions. Like I said above they are a useful tool to have when tuning, but if you do not have one shops that have dynos can hook up a wideband to tune your car with for an additional fee. Personally I don't see the need for a wideband for just an intake & exhaust, but getting one now will get it out of the way for the future.