huh, i had a simular issue, turned out to be a combo of loose spark plugs and a blocked up flowmaster muffler. the insides of the muffler rusted apart and where literally blocking exhaust flow. ive since fix it, but stock ls1 with LT headers, ls6 intake, and 3200 stall has me currently at 301RWHP/314RWTQ. i recently ran a 13.9 @ 101mph at the motorplex. was happy since the best i ran in el paso before was 14.7 when it was completly stock. freakin el paso elevation.
so hey, are there any decent tuning shops lately in el paso? im abuot to do some work that really requires a tune. im still considering getting hp tuners with taxes, but a shop that can get me up and running would be nice too.