Beware the EPR readings in the 737-200. We once had blocked Pt2 inlet reading on both engines due foreign objects finding their way into the sensor tubes. OAT 30C. Obviously not ice. On take off both EPR digital read-outs were equal at 2.18 EPR but somewhere along the take off run it was apparent that the acceleration was not normal for the indicated EPR.
In the darkened cockpit and with a very short runway and as all needles were identical on both engines, no one took a long hard look at the N1 indications. When it was obvious that we were never going to get airborne before the end of the runway, the captain firewalled both engines, rotated quickly, and got airborne at Vr minus 10 knots. On firewalling, both EPR leapt to around 2.27 (max allowable 2.18). Investigation revealed that in all probability, the actual N1 during the take off run was around 89% when for the conditions that night it should have been 101% N1 for 2.18EPR.