My 1995 WRX runs fine, but after about 30 mins driving, it runs lumpy, jolting, misfireing and udriveable.

After 5-10 mins it clears and runs sweet again

Fault code 23 - air flow, came up, replaced maf, but the problem is still there

Any ideas?

Thanks

 

Did you reset the ecu after replacing the maf? also id check the coil packs to make sure theres no cracks on any of them.

 

The coil packs are fairly new on his car, went in late last year

 

posssibly an air leak on the intake thats why it's coming up with that fault. check boost and vaccum hoses for leaks.
Dean.