P0171 and P0174 can be multiple things but usually caused by fuel trims that are greater than 15%, so a lean condition for one reason or other. Double check all the vacuum lines, PCV, anything after the MAF basically.
Anything with a soft sidewall to absorb shock and reduce the wheel hop is better on the IRS. I know broke7 on SVTP ran low 10's and got 1.5x or better 60fts with stock IRS and ET Streets (not radials).