Personally I am not using the default setups in either of these mods. So far in 1985 I haven't seen any significant difference between my car and the oposition. I have though faced the problem you mention in 1988 mod.
in my opinion there are three possible solutions to this.
1. Work hard and optimise the setup (takes a lot of time though and if you don't have enough it is a problem)
2. Use TSM to see the optimal setup for the track you're using or use other setups from other mods/seasons. usually this does the trick for me as it gives me a competitive car.
3. Edit the performance files, thus limiting the power and capabilities of the oposition (personally I do not recommend this)
Hope this helps