Oil pressure and pan vacuum would be a must. Pan vacuum will tell you a lot about the engines health or any issues. Oil pressure kinda goes without saying as you may catch something. FWIW we have the std channels that come with a Racepak voltage, 12volt event, RPM, Driveshaft RPM, both accelerometers then ad coolant temp, pan vac, oil pressure, oil temp trans pressure, trans temp, fuel pump pressure, fuel pressure, 8 O2's, rear shock sensors. As stated already it can become addicting but also takes a lot of guess work out. These channels and a good video camera will get you a LONG way quickly.