Please do not use Bosch plugs or O2's in your GM product. For some reason they have issues much more often than other brands. Denso is a great O2 and last I checked.. Rockauto had them for $35.
I've never heard of bosch problems, they're probably the best aftermarket for o2 sensors that I know of. I wouldn't buy their plugs though. Is denso the oem brand?
2006 Grand Prix GT S/C 109k - Modded Transgo Shift Kit, Gutted Airbox, Dash Cam, and Inlays. Retros soon to come. 2002 Grand Prix GT N/A 127k - Same as 06 Plus: Trans Cooler, DIY Aux Input, LED lighting, Suspension Upgrades, Tint, Retrofits. Sold.