Stick the standard grill back on deffo! It wont have any noticeable effect on airflow, cant see it being much worse at all!

As for when the T3 will run out of puff, I dont know maybe wont pull as hard from 6K onwards, total guess tho sure someone will know!

I've possibly got a T34.63 for sale in the next 4-6 months depending on what I do turbo wise, but if your interested then give me a PM.

I've stuck your car on the Series1 pic/regi database hope you dont mind!

https://passionford.com/forum/ford-escort-rs-turbo/76469-series-one-picture-database.html

I notice AVA modded your metering head, has it been there in the past?