The Dallara road course/street circuit/short oval bodykit, which alongside a dedicated superspeedway kit will replace the current manufacturer-produced kits from 2018, was run in a number of downforce levels at the 0.894mi oval.
Montoya and Servia tested set-ups ranging from a configuration which approximated the high downforce generated during July's Iowa race down to a downforce level 20 percent lower.
“It's interesting how you can run the same lap time and in one (downforce level) you're completely flat out and the other one you are lifting (off the accelerator in the turns),” Montoya, who again drove Chevrolet-powered Penske-prepared car, told IndyCar.com.
“We're trying to understand what's the best way to bring the best racing.
“When you run wide open (with higher downforce), the thing is like 7mph difference between the corners and the straight.
“The other one (with less downforce) is like 20 mph difference, so you get to see acceleration out of the corners and I think it's going to create better racing.”
Servia and Montoya also tested the ability to follow a car with the new bodykit, which generates more topside downforce and less underside downforce than the manufacturer-produced kits which will be discontinued at the end of the season.
The Spaniard, driving a Honda-powered Schmidt Peterson-prepared car, reported similar favourable results to those experienced in the first road course test at Mid-Ohio earlier in the month.
“I was able to run a decent distance behind Juan Pablo, and the car just loses a little bit of grip but (with) a four-tire kind of slide,” Servia told IndyCar.com.
“It's not like the front loses a lot of (grip) or the rear loses a lot, which is the problem with the current car.”
The Verizon IndyCar Series resumes at Pocono for the ABC Supply 500 on August 19-20.
The series will conduct its final test of the 2018 bodykit on September 26.