XEWA is rumored to only be running about 30 kw... it's still on the air only because the AM -> FM migration plan required migrants to keep the AM going if any listeners would be unserved were the AM to cease operation. Otherwise, they would have shut it off.
The same owner has lowered the power of its XEW, XEQ and XEX in Mexico City as well.
Interesting! Do you know how far XEWA got out back when it was 150,000 watts? I bet you could easily pick it up throughout the southern half of the US and down into Latin America!