My understanding is that it is only required when using a full size filter (Wix 51515). If the "shorty" is used (Wix 51085), the need is not as great. The problem IIRC was not interference with the exhaust, it was interference with the torsion bars. Normal engine movement would cause the end of a long filter to hit the bar and it was also tougher to get the long filter off. Personally, I've never had a LA engine A-body without a 90ยบ adapter, so I can't speak from experience.
