A very large number still do, even some of the field engines in the Permian run off the sour gas they move.
EPA has been chomping at the bit to regulate them and has been incrementally taking bits of control since 1995 (Title V).
But, “grandfathering” is saving many pipelines. The engines that provide NatGas from the Gulf to the Great Lakes were commissioned circa 1949 and still running like new today.
Despite their new(ish) Canadian ownership.
Very interesting!