Having impressed for the province's 'A' team in last week's win over the Ulster Ravens, winger Tuohy comes in to make his first Magners League appearance since last October.
Wynne slots in at outside centre, taking the place of the injured Niva Ta'auso (knee), while there are straight swops at half-back with Ian Keatley and Conor O'Loughlin on bench duty.
Up front, Robbie Morris, Bernie Upton, Mike McComish and Johnny O'Connor have been chosen to start.
With team captain John Muldoon unavailable due to a groin injury and his back row colleague Ray Ofisa also injured, McComish and O'Connor have taken their places in the starting line-up.
New Zealander Upton has been preferred in the second row to Connacht's record caps holder Michael Swift, while recent RBS 6 Nations debutant Sean Cronin has been included among the replacements.
Fellow Ireland international Gavin Duffy will captain Connacht in Muldoon's absence.
CONNACHT (v Leinster): Gavin Duffy (capt); Brian Tuohy, Aidan Wynne, Keith Matthews, Fionn Carr; Miah Nikora, Frank Murphy; Brett Wilkinson, Adrian Flavin, Robbie Morris, Mike McCarthy, Bernie Upton, Mike McComish, Johnny O'Connor, George Naoupu.
Replacements: Sean Cronin, Jamie Hagan, Michael Swift, Andrew Browne, Conor O'Loughlin, Ian Keatley, Troy Nathan.