revo software or not?

i have a 1997 a4 1.8t all stock and i went to wolfcars here in miami where they do the REVO software and flash your ecu supposedly he said id get like 30-35 horsepower and boosting 21psi!!!!!!!!!!!! isnt that alot? even though they sound like they know what trheyre doing...theyre a very respected german car product supplier here in miami but im not sure about that 21 psi of coarse once u get on it 21 but a constant of about 16 or 17? what do u guys think? should i do it? they do it in like 15 min