the oem heat shield doesnt bolt up to the new header. I noticed the temperature inside the engine compartment has risen a lot without the heat shield. is it ok to leave it like this or should i do something about it?

 

Should be fine, most after market headers do not allow the heat shield to be re-installed. If you have concerns there is a thread titled "How to get more air circulation under the hood" which has several good ideas and solutions to lower under hood temps.

 

what header is it?

 

A fit from Richmond... I put money on it being a T1R or J's

 

Insulate that A/C line going into the fire wall with insulation foam from the hardware store. It will keep the air ice cold.

 

You can put the OEM heat shield back on with stainless zip ties.

 

Or you can reuse the oem heat shield by welding threaded studs/tabs on the new header. Thats what I did.

 

I never noticed mine getting much hotter, are you sure it's not just the summer heat?