Question about headers and O2 senser
 

Does the O2 sensor have to be mounted in the collector?
I was telling a buddy about my car problems,
he suggested that I relocate the o2 sensor to one of the primaries. Has anyone tried this, did it work, where did you mount it to?

I've tried a heated o2 sensor, it made little or no difference at all.

Thanks.

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89 Formula, Maui Blue,355 TPI(used to be TBI) Auto, TES, 3" dynomax Hi-Flow cat, 3"Flowmaster single in, single out cat back. B&M shift kit, afpr.
89 Formula, Black, with really bad paint, 305 TPI Auto, t-tops bone stock (so far)

The only problem I see with mounting the O2 sensor in one of the primaries is that the computer will judge the lean/rich state for the entire engine solely on that one cylinder. I would think that this could result in very rich or lean conditions in some of the other 7 cylinders.

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Scott
88 GTA L98
14.389 @ 95.2 mph, 2.001 60'
In search of the elusive 1.9 60 foot time.

Sorry I haven't been able to respond sooner
I have this same concern, I was told that the o2 sensor was to far away from the hot
exhaust gases to get an accurate reading, What the sensor sees as a correct setting is actually to rich this is causing my plugs to foul and a hard start condition.

Would it help to increase backpressure at all?

A heated O2 sensor should solve your problem.
Various late-model GM vehicles used them.
Try an early 90's vette.

Installed one last week, haven't noticed much of a difference yet.

If you run a cooling system capable of keeping the coolant temperature below 170, you may not be going into closed loop completely.
Vader had some exact temperatures for various ECM functions at various coolant empertaure levels - check the archives.
A heated O2 should eliminate any questions about distance from the exhaust port and exhaust gas cooling.