Yes Alfie. In 1989 I finished 2nd to Dave Leach in the last of the old Production TTs. It was sadly the race that cost the lives of Phil Mellor and Steve Henshaw.
We had to ride on standard shocks, standard silencer, with lights still fitted. All that was removed was the side stand and the indicators and mirrors.
My bike was in the showroom at Allan Jefferies two weeks before the TT. We used one grade harder plug, one tooth smaller rear sprocket, and thicker oil in the forks.
Oh, we also replaced the fairing and seat which Loctite Yamaha supplied.
I would say that the bike was absolutely bog standard.
I set a new lap record at 117.27...........but it meant nothing considering what else happened during the race.
When the Production TT returned in 1996, you could replace the silencer (not the exhaust), and the rear shock..........something we had campaigned for in the 80s. Oh, AND you could remove the lights.
I actually loved riding Production bikes round there. I rode a standard K100RS, and a standard "jelly mould" CBR1000. Never finished lower than 8th. Great days, long gone.