GTA SA: Portal Through Interiors (PTI) is a modification that changes the algorithm of ENEX markers, from which they do not lead to the interiors that would be expected. For example, entering the Johnsons' house will take us to the Jefferson Motel, and entering the Pizzeria will take us to San Fierro in two seconds.
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Now we are in Shidoji's house: And now near the Jefferson Motel: