McGuinness was less than two seconds off his own record on Wednesday
John McGuinness set the second fastest lap time in TT history on Wednesday evenings practice, albeit unofficially.
The current record holder lapped the famous Mountain course in 17 minutes 23.46 seconds which is an average speed of 130.171 mph.
The Morecambe rider's time is just 0.183 seconds off his own official lap record set in 2007's senior race.
McGuinness said after his lap: "I don't know what to say really it just seems a bit mad at this stage."
Crowd favourite Guy Martin and Steve Plater also upped their pace recording 129.168 and 128.543 mph laps respectively.
Ian Hutchinson set the quickest overall Superstock time at 126.84, with Keith Amor slotting into second on 126.76.
Michael Dunlop recorded the fastest Supersport speed of the week with a 125.08 mph on his Street Sweep Yamaha.
Nick Crowe and Mark Cox continue to lead the sidecars on their HM Plant Honda machine, setting the fastest time of the week with a superb 116.063 mph lap.
Luis Carreira was the quickest newcomer putting in two laps above 118 mph and the event's only solo female competitor Jenny Tinmouth recorded a 107.415 mph lap.
Ollie Linsdell came off at Glen Duff and was taken to hospital with a fractured femur.
The final two practice sessions will be held on Thursday and Friday evenings.
Overall practice leader board
1. John McGuinness (Honda) 130.17 mph
2. Guy Martin (Honda) 129.16
3. Steve Plater (Honda) 128.45
1. Ian Hutchinson (Honda) 126.84 mph
2. Keith Amor (Honda) 126.76
3. Cameron Donald (Suzuki) 126.43
1. Michael Dunlop (Yamaha) 125.08 mph
2. John McGuinness (Honda) 123.10
3. Ian Hutchinson (Honda) 122.97
1. Nick Crowe/Mark Cox (HM Plant Honda) 116.063 mph
2. Dave Molyneux/Dan Sayle (A&J Racing Suzuki) 114.697
3. Phil Dongworth/Gary Partridge (WAS Autocentre Honda) 112.400