Hi, I'm new to this forum, I have a 1986 westy and I was getting poor gas milage (12.5 avg.) because of a bad O2 and cat. (O2 also unplugged), so I decided to replace my blown out cat and replace oxygen sensor with new Bosch replacement direct from "cost plus 10 program at GoWesty" Installed both and now the van runs like a clamp is placed on the fuel line in the first couple thousand RPMs of all gears. Its worst when cold and gets slightly better when at temprature, but not acceptable for a daily driver, I crawl from traffic signals. When I unplug the O2 sensor It runs fine in all conditions? Any suggestions? Thanks.