I've just fitted a new air filter it's a Heat shielded type. It was a universal one that i found quite cheap. I made the pipe work myself ( Shinney St/ Steel) and oviously retainted the MAF meter. After 15 miles of running the car tonight the engine management light came on. The car didn't run very well to start with but got better with miles. I have now put the original air box ect. back on but they light is still on, Any ideas!

 

I wonder if you've knackered your MAF sensor. They don't particularly like induction kits at the best of times, but a "universal type" with home-made pipe work... The first thing you need to do is find out what the CEL error code is. What MY is your Impreza?

That sounds suspiciously MAF related as well...

 

If MAF sensors don't like induction kits why do people fit them and how come no one else has this problem. The pipe work was copied from a HKS kit.
Oh it's a 01

 

Induction kits are fitted for one or more of the following reasons (plus more I've missed, no doubt)...

- The engine components have been modified beyond the scope of the stock air box.
- The ECU has been replaced with one that no longer requires the MAF.
- The owner wants the increased induction noise.
- The owner is under the illusion that mod alone will massively increase performance...

Obviously I'm lying like a cheap rug. You're the only person in the entire world with this problem, as induction kits have never damaged MAF sensors through vibration before.

Ah well, that's different then. I wish you'd said that in the first place. It's bound to be OK then. Ignore everything I've said.

Unfortunately that means you can't perform an ECU check yourself. You'll have to take it to a dealer, or find someone near you with Select Monitor...