I've had one aluminum contact cap, ended up replacing it not too long after installation, tracing was one of the issues, maybe it had thinner plastic in the body. I have learned that the TBI does not care for any multiple electrode plug, platinum etc., have had best luck with ACDelco CR43TS
My plow truck started running bad. I mean so bad it would hardly pull itself around. Cap was tracked all the way around inside. Suprised it ran at all.