As you know, a LT-1 Caprice and Impala SS have the same engine. If the Caprice was a 9c1, it had a real oil pressure gauge. ImpalaSS's do not, so that is a possible source of the problem with that. There is a thread here somewhere about how to install a 9c1 gauge in an SS and you may want to consider doing that. Good luck.
'95 9c1, pcmperformance.com 93 tune, Dynomax Ultraflo catback, K & N box filter, LT4 KM, 160 stat, 3.08 Posi.