Yes, guajillo chili is the best substitute you can use instead of pasilla. You can find guajillo in specialty shops and supermarkets. In terms of the amount of heat it gives off, the pasilla pepper is relatively close to the guajillo with a SHU of 1000- 2500 SHU to 1000- 1500 SHU. Both taste good, but guajillo has a fruity feel, while pasilla tastes more like raisins and cocoas.