It's the rear diff fluid and the under drive in the rear is compounding the problem.
With the standard gears in the car and 4k in the rear the throttle trigger will get touchy. It hasn't mattered what gear is in the rear with 3k, it's just about un drivable.
Try 7/7/5 with kit stock gears.
I start with 10/10/6 everywhere, standard ring&pinion.