It was a mustang dyno for sure (dyno jet). Thats the only cars that were there. So you think the readings could be off?

 

If it was a mustang brand dyno, and you ran in 2nd gear, and you are running heavy 22" wheels - then your numbers are more in line. If you had stock wheels and ran in 3rd gear on a dynojet, you'd probably see 30 more rwhp. Obviously it wouln't be making 30 more rwhp, its just a different test with a different result on the same vehicle.