Help: Failed NOx test in MA 1990 300SE

Good Old MA dyno testing gets me

Grams Per Mile
Reading Limit
HC 1.06 2.00
CO 5.86 30.00
NOx 4.17 3.00
CO2 359.26 N/A

Car Details:
1990 300SE 228,000 Miles
Car was running hot little over 100C
Only had mid grad gas in it 89 octane
Car sat idling for 5-10 mins before being tested

Cap, rotor, plugs, wire, filter, EGR valve replace less than 30,000 miles ago
Cat. was replaced back in 96 or so at 70,000 miles

Does the car need a new cat. system?

Or should I retest using premium gas and when it is running cooler and not allowed to idle so long before the test?

I have one more shot before I have to pay another 29 bucks.

Thanks
Dan