Unusually tach problems

[boosted99_420]

I have a strange tach problem i have never had so it makes it hard to see what my HX35 is truly hitting max boost at. I checked everything only thing i can think of is the noise sensor thing is going bad on it. The car is a 1990 AWD Talon with ECMlink v3 . The problem is when driving and i start getting on the throttle to 4k rpm it dies out and falls off. But when i slow down and the RPM goes below 4k it works again. The guy i bought the car from did put i giant Autometer tach in there also and im asuming wired it into the tach it self because while driving normal it goes crazy all the dang time. I am going to remove it and see if it may be the cause of the problem but im not 100% sure it is if anyone else has an Idea i am all ears on this one.

 

[GRAVEDIGGER]

I bet it's that 1990 cluster... They act weird when using a newer ecu. I think you have to switch a couple pins on the main ecu harness, the power transistor and coil pack (they're different on the 1990 too), and the tach within the guage cluster. I'm sorry I don't know exactly which wires to change, but that's the general idea of what I think you have going on. Good luck!