You seem to have the right bits to sort out much of the understeer, so I'm a bit surprised that you still have issues.
What arbs are you running and if they can be adjusted, what settings are you running on the front and rear?
Tyres play a big role in front end grip, so would be good to know what you have all around and what condition they are in?
Obviously things like tyre pressure, condition of the suspension bushings and tracking all play a huge role, so you need to know that they are sorted too.
Finally, one thing that may be the problem is your style of driving - using the accelerator to bring the rear out with this car will only result in more understeer, unless extensive mods are carried out. One of the best pieces of advice I was given once is to use the fact the this car is front-heavy, so the way to keep the grip at the front is to brake hard and deep into the corner even as you turn in. I know it sounds wrong (not only in an adult movie kind of way), but this was advice I got from a former F1 test driver at advanced car handling course. The idea is to use the weight of the engine to push down on the front wheels and increase their grip as you turn. This made the weight shift from the rear and cause it to come around like in a RWD car, but by using brake rather then throttle. This means that your entry speed is much faster into the corner and you can use the superior grip of the AWD system to accelerate out of it faster than you normally can in a FWD or RWD with similar power.
All that has to be practiced in a controlled environment and you have to have some understanding of how grip is affected by lateral forces in the corner when combined with weight transfer and application of brake or accelerator. I lost count how many times I spectacularly spun out while practicing this technique, but in the end I went from being barely able to take a fast corner at 60mph without running massively wide (due to exactly what you were doing with accelerator mid corner) to going through it at 90mph with the rear doing much of the turning and holding the steering wheel with my index finger. This was obviously in a controlled environment, on an airfield, but the same technique can be applied at road speeds to have much more control over the car in the corner. Best £250 ever spent on the car! Was a present from the wife
Whatever you do from this point is avoid touching the accelerator in the corner in your car and you will see it turn better assuming your car is setup correctly. See if you can go to one of these training days and you will be amazed at the difference some basic training will do to your driving - Car Limits is who I used.
