iNES Mapper 158 represents Tengen's board 800037, used for Alien Syndrome.
It modifies RAMBO-1 (mapper 64) in the exact same way that TLSROM (118) differs from MMC3 (4), by which we mean the RAMBO-1's CHR A17 output is connected to CIRAM A10.
Nestopia-1.4.0's implementation looks incomplete; it seems to ignore bank registers 8 and 9, as well as the K bit.
Categories: MMC3-like mappers, INES Mappers, In NesCartDB, Mappers with scanline IRQs, Mappers with cycle IRQs