C5 Z06 lap time change by adding a wing and splitter

Hi, I have a C5 Z06 track car.  Stock aero except for trac spec hood vents and a Blainefab adjustable spoiler.  What kind of change in lap time could I expect by changing the spoiler for a medium downforce Nine Lives wing and a plywood splitter made like the Nine Lives template?  The tracks I have data from are Road America, Blackhawk farms, and Brainerd.  It seems everyone I talk to says ~ 2 sec /lap.  Is this in the ball park?  I know it's a strange question, and I am ok with educated swag's.  Thanks in advance.

I would expect at least that much, possibly more. I picked up 2s with my Car of Tomorrow wing on a kart track with a lap time of 61s and an average speed of 44 mph. 

Thanks for the confirmation.  I think I need to add this to the short list for improvements.

Careful with a splitter on a C5. You have to make sure it can still get enough air through the radiator.