TL90 Weak PTO power

2001 TL90 PTO power seems weak, can only take a small bite with snow blower and earlier while brush hogging, noticed main pto slowing down before slip clutch to mower slipped, motor rpm's normal, no power pull down before pto slows. Checked hydraulic oil, pulled pto "on" solenoid, checked spool, very clean, o- rings, spacers seem fine. Installed gauge on hydraulic line T fitting right at inlet to PTO, have 160#psi @ 1500 + rpm. Have read low pressure should be 247-275#psi??? Could this low pressure be not locking clutch up fully? And if so, how do you increase it? Thanks, must fix before we get another 5' snowstorm in Buffalo N.Y.!!lol

TL90 Weak PTO power