I kind of had that happen to me but I embraced my new class by going pretty much all out with the mods. I know that modified mustangs never win street mod when going against Bmw's and evo's etc.
I started with a stock V6 mustang. I went and tried autocrossing in novice and loved it. I had a ball joint that was wearing out and decided to go with steeda X2 balljoints, sport springs and a bumpsteer kit. I figured if Im going to replace the ball joints I might as well improve something.
Well after reading the rules We figured out that changing the balljoint"changed the suspension geometry" which technically would put me in SM. I know some people change out the balljoints and stay in ESP.
Since we interpretted the rules that way I decided to take full advantage the SM rules. If I was going to run i was determined to become competitive.
So I went all out. The rules allowed up to 6liters na or 4 liters forced induction, so we installed a Vortech Supercharger. Next came caster camber plates, Subframe connectors, Tokico Illuminas, adjustable rear sway bar, strut tower brace, tloc,and 4.10 gears.
The car still handled badly, pushed in every corner, and I did some really cool donuts.
Why did all that money not improve the car? Because the two things that make the biggest difference in AutoX werent fixed yet.
My Driving and Tires.
Im kind of lucky I guess In one aspect. Glenn and I auto X in the same region. And he proves that you can autoX competitively in a SN95 mustang. Riding in his GT is better than a rollercoaster and cheaper too
He pointed out that to make a car as heavy as ours compete with the smaller lighter cars, we need big sticky tires.
So I make the plunge and bought kumho race rubber all around V700 ectas
265 35/18 up front
Tires made a HUGE difference. Better handling, braking, traction.
My driving wasnt keeping up with my mods, I could never learn how to drive the car because everytime i went to the track, It was a different car( This whole Modification thing happened over one season of Auto crossing.)
I started spending a lot of time with the driving instructors and had them make some reccomnedations on how to set up the car(i have adjustible shocks and a rear swaybar) and more importantly ponit out my mistakes.
Just learning to enter slaloms earlier took 2 seconds off my times.
The other big problem i had was braking, The brakepads I had really wasnt cutting it. When I switched to hp+ I saw another seriuos reductions in my times as I could break later and maintain my momentum.
As the car's handling got tighter I decided its time for more power. So I recently perfomed a split port swap(+40 or so hp) Installed a meth/water injection kit, installed a 2.87 vortech pulley(more boost) . I hope to get it finished shortly and get back to the track.
I also changed out all the bushings to urethane ones.
I havent won my class at an AutoX yet..But Im ususally not last anymore
and Im having a blast.