Do not adjust the Throttle Valve cable in an attempt to change shift quality or timing. You can F-up your transmission.
The TV system in the 4L60 (in 1990, the transmission became the 4L60, it was no longer a "700R4") is critical to establishing the correct pressure at the correct throttle setting. It is not a "kick down cable". It is not a "shift adjustment". It controls Line Pressure based on specific throttle opening. If pressure is low, clutches can slip and burn. This transmission has been around for 40 years, and there are still people that don't understand the importance of the TV system. Like the "mechanic" that adjusted the cable to adjust "shift quality".
The really easy way to know if your TV cable setting is correct: Shifter in D4. Leave at light throttle from a dead stop. Let the trans upshift into 2nd. As soon as it shifts, NAIL IT, all the way to the floor. The transmission MUST downshift back into 1st gear. If it does not, the TV cable is not adjusted correctly. FIX IT!
The LHM SyTy transmission has a really harsh 1-2 shift. It's a character of the SyTy.