Hideeho
I haven't been on in a few days (building a new track layout & then racing it). I'm weighing in a few items discussed in the last few days, sorry if I'm bringing back up stuff others thought done.

Slipper:
I have not tried the vts or the triad & haven't seen anyone local run them yet, so I only have to the info here to go on. The reason to change from the standard slipper pads are 3 fold; durability (how long between adjustments & maintenance), adjustability (what the range of useable adjustment is), & weight. The stock slipper REALLY falls down on durability. It needs to be adjusted multiple times a race day & needs maintenance at least after every practice/race day. The stick adjustability is ok, but still lacking. Weight is the base line for other comparisons. I have tried the white pad from the t4.1 & didn't care for it. It lacked adjustability, it is either on or off & 1/16 of turn either way turned it off. Durability seemed slightly better, but that may be because I kept stopping to adjust it to get it right & then didn't keep it on for very long. I also tried the hd pad from the sc10. I never could get it to slip to my liking. It being designed for the heavier truck, I don't think the b4.1 has enough weight to get the hd slipper to work properly, but if you like the slipper locked or close to it, that might be an option to try. From what I've read the VTS improves the durability by a little bit (same pad, just more of them) and the adjustability (if you have the right spring, b44 not b44.1) over stock but also increases weight, so it's a trade off. The triad seems to increase durability equivalent to the VTS (although I have read of a few people that have had issue with its durability), adjustment range seems to be better, & weight is less than the VTS. The only down side is you have to use avid spurs with it (considering avid quality & pricing right with other spurs I really don't see that as a down side, but some will). I am currently using the garodisk fron rc shox. The weight is a wash with stock (only pads are changed). Durability is through the roof! I have 4 race days & 3 practice days on it with ZERO maintenance to the pads (I am going to continue with no maintenance as long as I can just to see how far they can be pushed) & once I set it for a given track day it stays there ALL DAY with no adjustments & NO glazing. Adjustability us also incredible. I have about 1.5 turns of usable adjustment, that means if you are changing spurs on a race day & are pressed for time it is very quick to get set at a usable amount if slip, but if you have time you can easily get the slipper dialed to exactly where you want it. As an added bonus for those that have the VTS & triad mantis has VTS garodisks available & the triads are on ore order now.

Added weight:
Adding weight is us rather anathema to me (I'm a huge fan of Collin chapman!). When you can't move a component to adjust weight distribution, then add weight to balance it. Other than that, remove all weight possible & then add weight back where you want it to get back up to minimum weight for the class. If you are over minimum weight don't add more. Every gram on the car slows your acceleration by a little, makes you decelerate a little sooner & makes you carry a little less speed through corners. I can hear people already saying, "adding weight to front of my buggy really plants the front end." What you are doing by adding weight to 1 end or the other is changing your roll center & roll rate, both of which are better accomplished by changing your camber links. If you absolutely have to move weight to get your car balanced, move the battery then move the ESC & receiver, but adjust your camber links 1st.

Servos:
The only servos that seem to have regular issues are Savox, but that is depends more on the receiver & ESC. If you have a castle ESC replace it. It is decent & bullet proof, but inefficient, bulky, lacks adjustability, & means you all but have to use connectors for the motor. There are several better options for racing in the price range (viper, brushless hobbies, hobbywing, speed passion) & for slightly more there are even more (tekin, LRP). Spektrum DSM1 receivers also have issues with Savox servos, but not DSM2 receivers (& presumably DSMR when those hit). If you have a DSM1 receiver &/or don't want to change your castle ESC you will need a glitch buster cap to plug into any open slot on your receiver (never a bad idea regardless of your servo/receiver/ESC) & you will not have any issues.

Pushing under power:
Try loosening your dif a little (don't forget to reset the slipper). Iirc the battery was full forward, try moving it back 1/2 way then full back. Try 1/2* more camber in front. Try 1/2* less camber rear. Shorten the front camber link, lengthen the rear camber link. Raise the rear ball stud. Lower the front ball stud. Depending on where you are currently you may have to reverse the advice for the camber links & ball studs. Do 1 change at a time & drive at least 5-10 laps between each change. Iirc it handled well everywhere else but pushed on power coming out of tight corners, if this is the case I expect the dif will fix it (I am assuming your dif works properly & is smooth).