My cousin Joe just bought a '90 Talon TSI. I know very little about these cars. He let me drive it and it makes full boost (10psi) at about 2500rpm's and climbs to about 4500rpm's then it stops making power, like it hit a wall and runs very rich. He has an RJC boost controller and well, that's all I could ID on this thing. For the most part I understand it's stock. Have any idea's or can you guys help point him in the right direction, like web sites to search for answers?