quick ?
Sims are optional in a way. You have 3 options for the rears 1) Sims 2) Nothing and live with the SES light or 3) nothing and have the SES codes tuned out.
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But not much difference than the specified O2s would be, so if you need O2s, I would go with these rather than the reg length ones. The Best V8 Stories One Small Block at Time

