Hooker Nigel Conroy's sin-binning for a cynical ruck punch in first-half injury time had threatened to derail the Limerick men, and ex-Colomiers flanker David Tafanel's try on the restart did see Shannon go 17-12 in arrears.
'Tarf had ended a first half dominated by four David Delaney penalties for the home side with a dubious Bernard Jackman try in the left corner, but the crucial brace from Keogh and Ireland Sevens cap Tuohy helped Mick Galwey's men remain top.
Elsewhere, Garryowen railroaded into second on the back of a stirring 28-5 win over Cork Constitution.
Scrum-half Gerry Hurley put in an exhibition of pivot play at Dooradoyle, helping winger Billy Treacy (2) and fly-half Alan Purcell to tries.
Hurley kicked eleven points in all, with former Ireland Under-21 Andrew Finn converting Treacy's second effort in the closing minutes. Cronan Healy had answered back for a lacklustre Con on 46 minutes, jetting onto an early second half grubber from Conrad O'Sullivan.
At Belfield, two second half tries from centre John 'Grumpy' Anderson saw Belfast Harlequins dwarf UCD's play-off hopes. The students - 22-17 losers - lie nine points off fourth-placed 'Tarf and almost certainly out of contention for next month's semi-finals.
Eoghan Hickey's drop goal was all UCD had to offer in the first-half and although both Stephen Grissing and Brian O'Riordan touched down after the break, 'Quins were too good - with Ian Humphreys (12 points) to the fore.
League veteran Richie Murphy continued his outstanding kicking exploits at Oak Park, by helping County Carlow to a 32-27 victory over Blackrock, and lifting the midlanders off the bottom.
Murphy kicked a stunning haul of five penalties, two conversions and a drop goal. At Eaton Park, Ulster's Scott Young grabbed a try hat-trick in Ballymena's 40-13 trouncing of Galwegians - in a game which marked former Ireland international James Topping's first outing since breaking his leg in October.
At Stevenson Park, lluckless Dublin University incredibly secured their fourth draw of the season - 15-15 with Dungannon. Matt Crockett bagged two tries for Trinity, with Gillan Carruthers and Indian international winger Ajay Subherwal (2) on target for 'Gannon.
Subherwal's second on 65 minutes - converted by Ireland Under-21 skipper Gareth Steenson - tied it up.
In Division Two, four second half penalties from the boot of Mark Connolly saw Young Munster net a sixth win of the season - edging promotion hopefuls Old Crescent 20-19 at Tom Clifford Park.
Dolphin continue to lead the way, thanks to their 27-22 reversal of Old Belvedere. Record AIL points scorer John O'Mahony did the majority of the damage for the Corkmen, kicking five penalties and a conversion.
Meanwhile, man-of-the-match Conor Quaid scored all of Highfield's points in their 13-10 defeat of Midleton - a try, conversion, penalty and drop goal - as they moved off bottom spot.
Greystones continue to chew up the best that Division Three has to offer them. They scored another four tries - with a hat-trick going to sometime Leinster squad member Rob Connolly - as Sunday's Well were dismissed 32-10.
'Stones - winners of last season's Division Three final - are averaging an incredible 35 points-a-game.
AIB League: Results: March 26-27
Ballymena 40 Galwegians 13, Eaton Park County Carlow 32 Blackrock College 27, Oak ParkDungannon 22 Dublin University 22, Stevenson Park Garryowen 28 Cork Constitution 5, DooradoyleShannon 26 Clontarf 17, Thomond ParkUCD 17 Belfast Harlequins 22, Belfield
Barnhall 10 Malone 21, Parsontown Bective Rangers 16 UCC 20, Donnybrook De La Salle Palmerston 8 St Mary's College 32, Kilternan Midleton 10 Highfield 13, Town's ParkOld Belvedere 22 Dolphin 27, Anglesea RoadUL Bohemian 30 Thomond 3, Thomond Park Waterpark 24 Terenure College 17, Ballinakill Young Munster 20 Old Crescent 19, Tom Clifford Park
Ards 25 Connemara 21, Hamilton Park Clonakilty 24 City of Derry 3, Shannonvale CrossOld Wesley 17 Corinthians 11, DonnybrookQueen's University 21 Bruff 29, Dub LaneSkerries 27 Banbridge 16, HolmpatrickSunday's Well 10 Greystones 32, Musgrave Park Suttonians 35 Ballina 10, John J MacDowell ParkWanderers 10 Instonians 39, Lansdowne Road