Weight for stock ST
So my local track just started a 17.5 blinky ST class and I have been getting my but handed to me. My truck was really good in mod and I would normally finish in the top three of the A main. Now I'm lucky if I finish top three in the B main. My question is does weight really make that big of a difference? This is my first stock class so I am completely ignorant. My truck currently weighs in at 2110 grams. I am running a Trinity D4 1S 17.5 with a Reedy blackbox set to blinky. I'm geared 28/78 and running saddle packs. I'm debating on lighting up my truck and adding the three gear. Is it worth the investment. Or is there other things I could do?