O2 sensor... yay or nay again??
 

Top end recently rebuilt, no CAT (straight bypass pipe), new Bosch universal O2 sensor about a year ago, Steve Wong 91 oct premuffler chip, M&K muffler..... otherwise a stock 3.2.

I swear it runs ever so slightly better with the O2 sensor unplugged. Idle is just a tad smoother that makes it feel perfect. Acceleration and MPG's are about the same whether it's plugged in or not.

So..... any reason to keep it plugged in? Am I really going to affect the performance without it (remember, no CAT to worry about).

Part throttle (and idle) mixture will change with the O2 sensor. Keep in mind the change is more of a trim (slow change over time) rather than an instant event. It takes several seconds for the O2 sensor signal to move the mixture leaner or richer based on what it "sees". So the most impact is during cruise at constant speeds.

Just remember that some performance chips add fuel to get away with more aggressive timing. And that is true even in part-throttle maps. The O2 sensor negates that by moving the trim. So in part-throttle it all depends on what you end up perceiving as the better performance. In wide-open throttle it doesn't matter either way.

Your SW chip is likely mapped according to the presence of your O2 sensor (or no O2). You can check with Steve.