No, the beauty of the MFi RST engine (as in your escort) is that your metering head sorts it's self out as far as air/fuel ratios are concerned....

If you had an FRST and added zorst and filter you'd get nothing untill you chipped it, but add a zorst and fitler to your rst and it immediately runs more air in and more air out thus creating power. Reason is you increse the air in the metering flap opens more to compensate with fuel.

So by upping the boost it runs more fuel, lowering boost it runs less fuel.

Switching between the two is not a problem