A question about a recipe: Mumbai 'ishtyle' Pao Bhaji

Sumac wd be perfect.. (you just answered a niggling doubt of mine about some sumac I picked up from the Union sq holiday market, it was racking my brains to figure out what familiar ingredient it tasted like.. Aamchur! Thank you!!)..Lime juice is squeezed just before eating. it serves as a finishing ingredient in terms of aroma..tartness comes from the tomatoes as well..

Fabulous! Gosh, that was quick. What's a good substitute for raw mango powder? Sounds like something rather tart . . . what about sumac? Or lime juice added to the dish itself? Thanks so much!! ;o)

oops I meant commercial.. drat the spellcheck!

I've never made my own spice blend, but here's a link to a recipe that seems to include all the ingredients that are listed on the packaging of the commerce blends. hope this helps!
http://indianfood.about.com/od/masalarecipes/r/pavbhajimasala.htm