problems with boost gauge!!!

[turbodsm87]

my friend has a 91 talon turbo with an automatic. he put a 14b turbo on itr and has 2 1/2 in custom exhaust.we just put on an autometer boost guage but we keep getting funny readings out of it.crusing down the high way it reads 8-10psi but at about 6000rpm it spikes to 18-20 psi . i know this is not right on a stock motor. the car does not have a boost controller and it is all stock except fot the mods metiond in the begining.

 

[donmagicjuan]

Does it read 8-10 psi when you're at constant speed on a level road? Also, knowing where you tapped your boost gage and what it reads at idle might be helpful.