I need help finding the problem with a significant power loss. Its an 85 GSL 12A with 108k miles. Changed fuel filter, tune up, removed front cat from the header and still had power loss. I got denso spark plugs, could that be it. Thanks

 

Check for spark at all 4 plugs. Before I had a similar problem and it actually ended up being the leading ignitor had gone. The result was no leading spark, HUGE power loss...

 

How would I check for spark, do I remove cable from spark plug and check that way.

 

I used a timing light on the plug wires. If your are turning the engine over with one plug removed you are asking for a fire to start. Compressed air, + gas = bad thing when it's not contained inside of the engine.

 

Could I be losing compression, car starts fine and steady for the first minute then it starts to misfire.

 

Open up the carb hat, start the car and see if fuel is being dumped in. If you see droplets rather than mist it's your carburator.