You may want to look elsewhere for the lag cause. When I ran the 4-row my lag stayed the same, however power went up dramatically in the mid-range all the way to peak rpm.
Is your turbo outlet pointing straight down to take advantage of the 4-row piping. The 3-row piping has several bends including a 180 degree one off your turbo. The piping also necks down to 2" as it goes through the fender. This causes lag on the 3-row.
Do you have an AEM where you can view timing? Timing retard can cause lag, turbo wheel damage can cause lag, pressure leaks from turbo manifold or in intake system can cause lag, minor piston damage where the ceramic flaked off will cause lag if you're running a stock ECU because the stock ECU will pull out timing as a result of knock noise. A leaking BOV will appear to cause lag. Too big an A:R on the turbo will cause lag.
These are just a few of the places you might want to look.
In my experience the 4-row is better for cars over 600rwhp under 2,000 ft elevation, and over 700rwhp between 2,000-4,000 ft elevation.
Take care,
Chris.